Updated on 2021/12/21

写真a

 
ICHIOKA Masanori
 
Organization
Research Institute for Interdisciplinary Science Professor
Position
Professor
External link

Degree

  • Doctor(science) ( Kyoto University )

Research Interests

  • 物性理論

  • electronic state

  • spin & charge density wave

  • superconductivity

  • vortex state

  • Theory of condensed matter

  • 電子状態

  • スピン電荷密度波

  • 超伝導

  • 磁束渦糸

Research Areas

  • Natural Science / Magnetism, superconductivity and strongly correlated systems

Education

  • Kyoto University   理学研究科   物理学第一

    1989.4 - 1996.1

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    Country: Japan

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  • Kyoto University   理学部  

    1985.4 - 1989.3

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    Country: Japan

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Research History

  • Okayama University   Research Institute for Interdisciplinary Science   Professor

    2016.4

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  • Okayama University   Department of Physics   Professor

    2011.4 - 2016.3

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  • Okayama University   Department of Physics   Associate Professor

    2007.4 - 2011.3

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  • Okayama University   Department of Physics   Associate Professor (as old post name)

    2003.1 - 2007.3

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  • Okayama University   Department of Physics   Research Assistant

    1998.9 - 2002.12

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  • Japan Society for Promotion of Science   Research Fellowship for Young Scientists (DC/PD)

    1996.1 - 1998.8

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Professional Memberships

Committee Memberships

  • 日本物理学会   第75~76期代議員  

    2019.4 - 2021.3   

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    Committee type:Academic society

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  • 日本物理学会   領域6(金属・低温)代表  

    2018   

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    日本物理学会

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  • 日本物理学会   領域6(金属・低温)副代表  

    2017   

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    Committee type:Academic society

    日本物理学会

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Papers

  • Spin Hall effect generated by fluctuating vortices in type-II superconductors

    Takuya Taira, Yusuke Kato, Masanori Ichioka, Hiroto Adachi

    PHYSICAL REVIEW B   103 ( 13 )   2021.4

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:AMER PHYSICAL SOC  

    We theoretically investigate the vortex spin Hall effect, i.e., a novel spin Hall effect driven by the motion of superconducting vortices, by focusing on the role of superconducting fluctuations. Within the BCS-Gor'kov microscopic approach combined with the Kubo formula, we find a strong similarity between the vortex spin Hall effect and the vortex Nernst/Ettingshausen effect. Calculated temperature dependence of the voltage signal due to the inverse vortex spin Hall effect exhibits a strong enhancement by vortex fluctuations. This result not only provides a possible explanation for a prominent peak found in the spin Seebeck effect in a NbN/Y3Fe5O12 system but also leads to a proposal of new experiments using other superconductors with strong fluctuations, such as cuprate or iron-based superconductors.

    DOI: 10.1103/PhysRevB.103.134417

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  • Nonmagnetic impurity effect in vortex states of chiral superconductors

    Takahiro Ueda, Yasuaki Sera, Hiroto Adachi, Masanori Ichioka

    PHYSICAL REVIEW B   103 ( 1 )   2021.1

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:AMER PHYSICAL SOC  

    Nonmagnetic impurity scattering effects in the vortex states are studied in the Born and the unitary limits for chiral superconductors by Eilenberger theory. We compare the spatial structure of the pair potential and local electronic structure in chiral p-wave superconductors with those in two types of chiral d-wave superconductors; d(1 +/-) d(xz) +/- id(yz) and d(2 +/-) d(x2-y2 )+/- id(xy) pairing Similar behaviors of the pair potentials are seen in p +/- - and d(1 +/-) -wave superconductors. In chiral d-wave superconductors, due to lack of Majorana properties relating to the s-wave Cooper pair amplitude, zero-energy vortex bound states are easily destroyed by the impurity scattering, compared to the Born limit in the chiral p_-wave superconductors. This decay is also seen in the unitary limit in the chiral p_ -wave superconductors. These differences are also discussed in the relation to s-wave Cooper pair amplitude and the local scattering rate. The impurity effects are also compared with those in s-wave superconductors.

    DOI: 10.1103/PhysRevB.103.014506

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  • Vortex Cores in Narrow Thin-Film Strips

    Vladimir G. Kogan, Masanori Ichioka

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   89 ( 9 )   2020.9

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    We study vortex current distributions in narrow thin-film superconducting strips with the help of analytic expression of the vortex current derived within the London theory. Using definition of the vortex core "boundary" as a curve where the current reaches the depairing value, vortex core size and shape are estimated as a function of vortex position in the strip. We show that the core size near the strip edges is smaller than in the rest of the strip, indicating that the BardeenStephen flux-flow resistivity should be reduced near the edges. Moreover, at elevated temperatures, when the depairing current is small, the vortex core may extend to the whole strip width, thus turning into an edge-to-edge phase-slip line.

    DOI: 10.7566/JPSJ.89.094711

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  • Microscopic Eilenberger theory of Fulde-Ferrell-Larkin-Ovchinnikov states in the presence of vortices

    Kenta M. Suzuki, Kazushige Machida, Yasumasa Tsutsumi, Masanori Ichioka

    PHYSICAL REVIEW B   101 ( 21 )   2020.6

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    We theoretically investigate the Fulde-Ferrell-Larkin-Ovchinnikov state by using the microscopic quasiclassical Eilenberger equation. The Pauli paramagnetic effects and the orbital depairing effects due to vortices are treated on an equal footing for three-dimensional spherical Fermi surface model and s-wave pairing. The field evolution of the Larkin-Ovchinnikov (LO) state is studied in detail, such as the H-T phase diagram, spatial structures of the order parameter, the paramagnetic moment, and the internal field. Field dependences of various thermodynamic quantities-the paramagnetic moment, entropy, and the zero-energy density of states-are calculated. Those quantities are shown to start quickly growing upon entering the LO state. We also evaluate the wavelength of the LO modulation, the flux line lattice form factors for small-angle neutron scattering, and the NMR spectra to facilitate the identification of the LO state. Two cases of strong and intermediate Pauli paramagnetic effect are studied comparatively. The possibility of the LO phase in Sr2RuO4, CeCoIn5, CeCu2Si2, and the organic superconductors is critically examined and crucial experiments to identify it are proposed.

    DOI: 10.1103/PhysRevB.101.214516

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  • Spin pumping into a spin glass material

    Yusei Fujimoto, Masanori Ichioka, Hiroto Adachi

    PHYSICAL REVIEW B   101 ( 18 )   2020.5

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    Spin pumping is a recently established means for generating a pure spin current, whereby spins are pumped from a magnet into the adjacent target material under the ferromagnetic resonance condition. We theoretically investigate the spin pumping from an insulating ferromagnet into spin glass materials. Combining a dynamic theory of spin glasses with the linear-response formulation of the spin pumping, we calculate temperature dependence of the spin pumping near the spin glass transition. The analysis predicts that a characteristic peak appears in the spin pumping signal, reflecting that the spin fluctuations slow down upon the onset of spin freezing.

    DOI: 10.1103/PhysRevB.101.184412

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  • Variation of zero-energy density of states of a d-wave superconductor in a rotating in-plane magnetic field: Effect of nonmagnetic impurities

    Yuuki Hashitani, Kenta K. Tanaka, Hiroto Adachi, Masanori Ichioka

    PHYSICAL REVIEW B   101 ( 6 )   2020.2

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:AMER PHYSICAL SOC  

    Oscillation of zero-energy density of states under the rotation of an in-plane magnetic field is used to identify node positions of the superconducting gap. Based on Eilenberger theory that can capture the vortex core contribution appropriately, we quantitatively study the effects of nonmagnetic impurity scattering on the oscillation in a d(x2-y2) -wave superconductor, as a function of the magnetic field and the scattering rate in the Born and the unitary limits. We find that the sign of the oscillation can be changed by the impurity scattering at low fields, indicating that impurity effect is an important factor in the analysis of angle-resolved specific heat measurements.

    DOI: 10.1103/PhysRevB.101.060501

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  • Relation of Superconducting Pairing Symmetry and Non-Magnetic Impurity Effects in Vortex States

    Yasuaki Sera, Takahiro Ueda, Hiroto Adachi, Masanori Ichioka

    SYMMETRY-BASEL   12 ( 1 )   2020.1

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:MDPI  

    Non-magnetic impurity scattering effects on the vortex core states are theoretically studied to clarify the contributions from the sign-change of the pairing function in anisotropic superconductors. The vortex states are calculated by the Eilenberger theory in superconductors with px-wave pairing symmetry, as well as the corresponding anisotropic s-wave symmetry. From the spatial structure of the pair potential and the local electronic states around a vortex, we examine the differences between anisotropic superconductors with and without sign-change of the pairing function, and estimate how twofold symmetric vortex core images change with increasing the impurity scattering rate both in the Born and the unitary limits. We found that twofold symmetric vortex core image of zero-energy local density of states changes the orientation of the twofold symmetry with increasing the scattering rate when the sign change occurs in the pairing function. Without the sign change, the vortex core shape reduces to circular one with approaching dirty cases. These results of the impurity effects are valuable for identifying the pairing symmetry by observation of the vortex core image by the STM observation.

    DOI: 10.3390/sym12010175

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  • Spin Seebeck effect in paramagnets and antiferromagnets at elevated temperatures

    Yutaka Yamamoto, Masanori Ichioka, Hiroto Adachi

    PHYSICAL REVIEW B   100 ( 6 )   2019.8

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    We develop a theory of the spin Seebeck effect (SSE) in paramagnets as well as in antiferromagnets at elevated temperatures where the classical limit of the fluctuation-dissipation theorem is applicable. Employing dissipative stochastic models that are valid at these temperatures, we calculate the SSE signal, and we find that both the paramagnetic SSE and the antiferromagnetic SSE are expressed by a single equation that is proportional to the external magnetic field times the spin susceptibility of the magnet. The present result suggests the appearance of a cusp structure at the Neel temperature in the antiferromagnetic SSE signal.

    DOI: 10.1103/PhysRevB.100.064419

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  • Paramagnetic Pair-Breaking in Spin-Triplet Superconductors with Spin-Orbit Coupling: Application to Sr2RuO4

    Koushi Oda, Kenta K. Tanaka, Seiichiro Onari, Masanori Ichioka

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   88 ( 6 )   2019.6

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    Paramagnetic pair-breaking effects by in-plane magnetic fields are studied in the presence of the spin-orbit coupling, based on the tight-binding three-orbital model for Sr2RuO4. The spin-orbit coupling interfere with the paramagnetic pair-breaking effects in the spin-singlet pairing and the spin-triplet helical p-wave superconductors. We show how the superconducting transition temperature T-c depends on the field orientation and the pairing symmetry. In the spin-triplet chiral p-wave superconductors, as the condition for that the paramagnetic pair-breaking works even to the in-plane fields, we need the mixing of different d-orbital electrons by the c-direction hopping, in addition to the spin-orbit coupling. We also study a case of the change from the helical to chiral p-wave states by the paramagnetic effect.

    DOI: 10.7566/JPSJ.88.064707

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  • Spin diffusion equation in superconductors in the vicinity of T-c

    Takuya Taira, Masanori Ichioka, So Takei, Hiroto Adachi

    PHYSICAL REVIEW B   98 ( 21 )   2018.12

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    We microscopically derive the spin diffusion equation in an s-wave superconductor in the vicinity of the superconducting transition temperature T-c. Applying the general relation between the relaxation function and the response function to the present spin diffusion problem, we examine how the spin relaxation time and the spin diffusion coefficient are renormalized in the superconducting state. The analysis reveals that, below T-c, both the spin relaxation time and the spin diffusion coefficient are increased, resulting in an enhancement of the spin diffusion length. The present result may provide an explanation for the recent observation of an enhanced spin pumping signal below T-c in a Py/Nb/Pt system that is free from the coherence peak effect.

    DOI: 10.1103/PhysRevB.98.214437

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  • Theoretical analysis for spin-polarized local density of states in the vortex state of helical p-wave superconductors Reviewed

    Kenta K Tanaka, Masanori Ichioka, Seiichiro Onari

    Journal of Physics: Conference Series   969 ( 1 )   2018.4

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    Language:English   Publishing type:Research paper (international conference proceedings)   Publisher:Institute of Physics Publishing  

    Based on the quasi-classical Eilenberger theory, we calculate the site-dependence of order-parameter and spin-polarized local density of states (LDOS) in the vortex lattice state of helical p-wave superconductors. The spin-polarized LDOS is induced around the vortex core by the vorticity coupling to the chirality of up-spin pair or down-spin pair. In order to distinguish the d-vector symmetry, we investigate the magnetic eld effect on the spatial structure of the spin-polarized LDOS.

    DOI: 10.1088/1742-6596/969/1/012043

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  • Local NMR relaxation rates T1-1 and T2-1 depending on the d -vector symmetry in the vortex state of chiral and helical p -wave superconductors Reviewed

    Kenta K. Tanaka, Masanori Ichioka, Seiichiro Onari

    Physical Review B   97 ( 13 )   2018.4

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:American Physical Society  

    Local NMR relaxation rates in the vortex state of chiral and helical p-wave superconductors are investigated by the quasiclassical Eilenberger theory. We calculate the spatial and resonance frequency dependences of the local NMR spin-lattice relaxation rate T1-1 and spin-spin relaxation rate T2-1. Depending on the relation between the NMR relaxation direction and the d-vector symmetry, the local T1-1 and T2-1 in the vortex core region show different behaviors. When the NMR relaxation direction is parallel to the d-vector component, the local NMR relaxation rate is anomalously suppressed by the negative coherence effect due to the spin dependence of the odd-frequency s-wave spin-triplet Cooper pairs. The difference between the local T1-1 and T2-1 in the site-selective NMR measurement is expected to be a method to examine the d-vector symmetry of candidate materials for spin-triplet superconductors.

    DOI: 10.1103/PhysRevB.97.134507

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  • Spin Seebeck effect in a simple ferromagnet near Tc: a Ginzburg-Landau approach Reviewed

    Hiroto Adachi, Yutaka Yamamoto, Masanori Ichioka

    Journal of Physics D: Applied Physics   51 ( 14 )   144001(1) - 144001(1)-144001(5)   2018

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:IOP PUBLISHING LTD  

    A time-dependent Ginzburg-Landau theory is used to examine the longitudinal spin Seebeck effect in a simple ferromagnet in the vicinity of the Curie temperature T-c. It is shown analytically that the spin Seebeck effect is proportional to the magnetization near T-c, whose result is in line with the previous numerical finding. It is argued that the present result can be tested experimentally using a simple magnetic system such as EuO/Pt or EuS/Pt.

    DOI: 10.1088/1361-6463/aab1d1

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  • Pair breaking of multigap superconductivity under parallel magnetic fields in the electric-field-induced surface metallic state

    Masahiro Nabeta, Kenta K. Tanaka, Seiichiro Onari, Masanori Ichioka

    PHYSICAL REVIEW B   96 ( 9 )   296 - 303   2017.9

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    The roles of paramagnetic and diamagnetic pair-breaking effects in superconductivity in the electric-fieldinduced surface metallic state are studied using the Bogoliubov-de Gennes equation when magnetic fields are applied parallel to the surface. The multigap states of the subbands are related to the depth dependence and the magnetic field dependence of the superconductivity. In the Fermi-energy density of states and the spin density, subband contributions successively appear from higher-level subbands with increasing magnetic fields. The characteristic magnetic field dependence may be a key feature to identify the multigap structure of the surface superconductivity.

    DOI: 10.1103/PhysRevB.96.094522

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  • Paramagnetic and diamagnetic pair-breaking effect in electric-field-induced surface superconductivity under parallel magnetic fields

    Masanori Ichioka, Masahiro Nabeta, Kenta K. Tanaka, Seiichiro Onari

    Journal of Physics: Conference Series   871 ( 1 )   47 - 55   2017.7

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    Electric-field-induced surface superconductivity is studied by Bogoliubov-de Gennes equation under magnetic fields parallel to the surface. We estimate the pair-breaking effects by the paramagnetic Zeeman shift and by diamagnetic screening current. We find that the depth dependences of pair potential, screening current, spin current, and paramagnetic moment under the magnetic fields reflect the multi-gap superconductivity in the sub-band structure.

    DOI: 10.1088/1742-6596/871/1/012001

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  • Spin-polarized local density of states around vortex in helical p-wave superconductors

    Kenta K. Tanaka, Masanori Ichioka, Seiichiro Onari

    Journal of Physics: Conference Series   871 ( 1 )   249 - 252   2017.7

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    Based on the quasi-classical Eilenberger theory, we investigate the magnetic field dependence of order-parameters and spin-polarized local density of states (LDOS) in the vortex lattice state of helical p-wave superconductors. The spin-polarized LDOS is induced by the vorticity coupling to the chirality of up-spin pair or down-spin pair, even when Knight shift does not change. We clarify the instability of the helical p-wave state at high field, and that the spin-polarized LDOS shows the unique behaviors of the helical p-wave state.

    DOI: 10.1088/1742-6596/871/1/012024

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  • Spin pumping into superconductors: A new probe of spin dynamics in a superconducting thin film

    Masashi Inoue, Masanori Ichioka, Hiroto Adachi

    PHYSICAL REVIEW B   96 ( 2 )   239 - 249   2017.7

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    Spin pumping refers to the microwave-driven spin current injection from a ferromagnet into the adjacent target material. We theoretically investigate the spin pumping into superconductors by fully taking account of impurity spin-orbit scattering that is indispensable to describe diffusive spin transport with finite spin diffusion length. We calculate temperature dependence of the spin pumping signal and show that a pronounced coherence peak appears immediately below the superconducting transition temperature T-c, which survives even in the presence of the spin-orbit scattering. The phenomenon provides us with a new way of studying the dynamic spin susceptibility in a superconducting thin film. This is contrasted with the nuclear magnetic resonance technique used to study a bulk superconductor.

    DOI: 10.1103/PhysRevB.96.024414

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  • Spin-polarized local density of states in the vortex state of helical p-wave superconductors

    Kenta K. Tanaka, Masanori Ichioka, Seiichiro Onari

    PHYSICAL REVIEW B   95 ( 13 )   23 - 40   2017.4

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    Properties of the vortex state in helical p-wave superconductor are studied by the quasiclassical Eilenberger theory. We confirm the instability of the helical p-wave state at high fields and that the spin-polarized local density of states M(E, r) appears even when Knight shift does not change. This is because the vorticity couples to the chirality of up-spin pair or down-spin pair of the helical state. In order to identify the helical p-wave state at low fields, we investigate the structure of the zero-energyM(E = 0, r) in the vortex states, and also the energy spectra of M(E, r).

    DOI: 10.1103/PhysRevB.95.134502

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  • Locking of length scales in two-band superconductors

    M. Ichioka, V. G. Kogan, J. Schmalian

    PHYSICAL REVIEW B   95 ( 6 )   1517 - 1523   2017.2

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    A model of a clean two-band s-wave superconductor with cylindrical Fermi surfaces, different Fermi velocities v(1),(2), and a general 2x2 coupling matrix V-alpha beta is used to study the order parameter distribution in vortex lattices. The Eilenberger weak coupling formalism is used to calculate numerically the spatial distributions of the pairing amplitudes Delta(1) and Delta(2) of the two bands for vortices parallel to the Fermi cylinders. For generic values of the interband coupling V-12, it is shown that, independently of the couplings V-alpha beta, of the ratio v(1)/v(2), of the temperature, and the applied field, the length scales of spatial variation of Delta(1) and of Delta(2) are the same within the accuracy of our calculations. The only exception from this single length-scale behavior is found for V-12 << V-11, i.e., for nearly decoupled bands.

    DOI: 10.1103/PhysRevB.95.064512

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  • Pair-breaking effects by parallel magnetic field in electric-field-induced surface superconductivity

    Masahiro Nabeta, Kenta K. Tanaka, Seiichiro Onari, Masanori Ichioka

    PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS   530   8 - 10   2016.11

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:ELSEVIER SCIENCE BV  

    We study paramagnetic pair-breaking in electric-field-induced surface superconductivity, when magnetic field is applied parallel to the surface. The calculation is performed by Bogoliubov-de Gennes theory with s-wave pairing, including the screening effect of electric fields by the induced carriers near the surface. Due to the Zeeman shift by applied fields, electronic states at higher-level sub-bands become normal-state-like. Therefore, the magnetic field dependence of Fermi-energy density of states reflects the multi-gap structure in the surface superconductivity. (C) 2016 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.physc.2016.04.006

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  • Effects of vorticity and impurity on NMR relaxation rate in chiral p-wave superconductors

    Kenta K. Tanaka, Masanori Ichioka, Seiichiro Onari

    PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS   530   62 - 64   2016.11

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    In order to study site-selective NMR in chiral p -wave superconductors, we calculate local nuclear relaxation rate T-1(-1) in the vortex lattice state by Eilenberger theory with and without non-magnetic impurity scattering in the Born limit and unitary limit. The local T-1(-1) in the NMR resonance line shape is different between two chiral states p(+/-), depending on whether the chirality is parallel or anti-parallel to the vorticity. In the p(-)-wave, anomalous suppression of local T-1(-1) occurs around the vortex core due to the negative coherence term coming from odd-frequency s-wave Cooper pair induced around the vortex. We especially examine the site dependence of the anomalous suppression of local T-1(-1), including the applied magnetic field dependence and the impurity effects. (C) 2016 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.physc.2016.03.003

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  • Site-selective NMR for odd-frequency Cooper pairs around vortex in chiral p-wave superconductors

    Kenta K. Tanaka, Masanori Ichioka, Seiichiro Onari

    PHYSICAL REVIEW B   93 ( 9 )   094507-1-094507-5   2016.3

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    In order to identify the pairing symmetry with chirality, we study site-selective NMR in chiral p-wave superconductors. We calculate local nuclear relaxation rate T-1(-1) in the vortex lattice state by Eilenberger theory, including the applied magnetic field dependence. We find that T-1(-1) in the NMR resonance line shape is different between two chiral states p +/-(= p(x)+/- ip(y)), depending on whether the chirality is parallel or antiparallel to the vorticity. Anomalous suppression of T-1(-1) occurs around the vortex core in the chiral p(-) wave due to the negative coherence term coming from the odd-frequency s-wave Cooper pair induced around the vortex with Majorana state.

    DOI: 10.1103/PhysRevB.93.094507

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  • Symmetry-Protected Topological Superfluids and Superconductors-From the Basics to He-3

    Takeshi Mizushima, Yasumasa Tsutsumi, Takuto Kawakami, Masatoshi Sato, Masanori Ichioka, Kazushige Machida

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   85 ( 2 )   022001-1-022001-74   2016.3

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    In this article, we give a comprehensive review of recent progress in research on symmetry-protected topological superfluids and topological crystalline superconductors, and their physical consequences such as helical and chiral Majorana fermions. We start this review article with the minimal model that captures the essence of such topological materials. The central part of this article is devoted to the superfluid He-3, which serves as a rich repository of novel topological quantum phenomena originating from the intertwining of symmetries and topologies. In particular, it is emphasized that the quantum fluid confined to nanofabricated geometries possesses multiple superfluid phases composed of the symmetry-protected topological superfluid B-phase, the A-phase as a Weyl superfluid, the nodal planar and polar phases, and the crystalline ordered stripe phase. All these phases generate noteworthy topological phenomena, including topological phase transitions concomitant with spontaneous symmetry breaking, Majorana fermions, Weyl superfluidity, emergent supersymmetry, spontaneous edge mass and spin currents, topological Fermi arcs, and exotic quasiparticles bound to topological defects. In relation to the mass current carried by gapless edge states, we also briefly review a longstanding issue on the intrinsic angular momentum paradox in He-3-A. Moreover, we share the current status of our knowledge on the topological aspects of unconventional superconductors, such as the heavy-fermion superconductor UPt3 and superconducting doped topological insulators, in connection with the superfluid He-3.

    DOI: 10.7566/JPSJ.85.022001

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  • Transverse Components of Flux Line Lattice Form Factors in Uniaxial Superconductors

    Masanori Ichioka, Yuujirou Amano, Masahiro Ishihara, Kazushige Machida

    PROCEEDINGS OF THE 28TH INTERNATIONAL SYMPOSIUM ON SUPERCONDUCTIVITY (ISS 2015)   81   77 - 80   2016

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    Language:English   Publishing type:Research paper (international conference proceedings)   Publisher:ELSEVIER SCIENCE BV  

    Magnetic field orientation dependence of transverse and longitudinal flux line lattice form factors are theoretically studied in uniaxial superconductors with extremely large anisotropy ratio 60 for some field magnitudes. The form factors are estimated by two methods, the Eilenberger theory and the London theory comparatively. We also compare them to the form factors observed by the small angle neutron scattering experiment on Sr2RuO4. We discuss the cutoff function of extended London theory, and the contributions from the suppression of the pair potential as a function of the field orientation. (C) 2016 The Authors. Published by Elsevier B.V.

    DOI: 10.1016/j.phpro.2016.04.031

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  • Hidden crossover phenomena in strongly Pauli-limited multiband superconductors: Application to CeCu2Si2 Reviewed

    Yasumasa Tsutsumi, Kazushige Machida, Masanori Ichioka

    Physical Review B - Condensed Matter and Materials Physics   92 ( 2 )   2015.7

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:American Physical Society  

    Motivated by recent experiments on heavy fermion materials CeCu2Si2 and UBe13, we develop a framework to capture generic properties of multiband superconductors with strong Pauli paramagnetic effect (PPE). In contrast to the single band case, the upper critical field Hc2 can remain a second-order transition even for strong PPE cases. The expected first-order transition is hidden inside Hc2 and becomes a crossover due to the interplay of multibandness. The present theory based on full self-consistent solutions of the microscopic Eilenberger theory explains several mysterious anomalies associated with the crossover and the "empty" vortex core state which is observed by recent STM experiment on CeCu2Si2.

    DOI: 10.1103/PhysRevB.92.020502

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  • Pauli paramagnetic effects on mixed-state properties in a strongly anisotropic superconductor: Application to Sr2RuO4

    Yuujirou Amano, Masahiro Ishihara, Masanori Ichioka, Noriyuki Nakai, Kazushige Machida

    PHYSICAL REVIEW B   91 ( 14 )   2015.4

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    We study theoretically the mixed-state properties of a strong uniaxially anisotropic type-II superconductor with the Pauli paramagnetic effect, focusing on their behaviors when the magnetic field orientation is tilted from the conduction layer ab plane. On the basis of Eilenberger theory, we quantitatively estimate significant contributions of the Pauli paramagnetic effects on a variety of physical observables, including transverse and longitudinal components of the flux-line lattice form factors, magnetization curves, Sommerfeld coefficient, field distributions, and magnetic torques. We apply these studies to Sr2RuO4 and quantitatively explain several seemingly curious behaviors, including the H-c2 suppression for the ab-plane direction, the larger anisotropy ratio and intensity found by the spin-flip small-angle neutron scattering, and the first-order transition observed recently in magnetocaloric, specific-heat, and magnetization measurements in a coherent and consistent manner. Those lead us to conclude that Sr2RuO4 is either a spin-singlet or a spin-triplet pairing with the d-vector components in the ab plane.

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  • Eilenberger theory for nuclear magnetic relaxation rate in superconducting vortex lattice state Reviewed

    Kenta K. Tanaka, Masanori Ichioka, Seiichiro Onari, Noriyuki Nakai, Kazushige Machida

    Physical Review B - Condensed Matter and Materials Physics   91 ( 1 )   2015.1

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    On the basis of the Eilenberger theory, spatial variation of the local NMR relaxation rate T1-1 is quantitatively estimated in the vortex lattice state, to clarify the differences between the s-wave and the d-wave superconductors. We study the temperature and the magnetic field dependencies of T1-1 inside and outside of the vortex core, including influences of nonmagnetic impurity scatterings in the Born limit and in the unitary limit. These results are helpful to detect detailed characters of local electronic structures in the vortex lattice states via site-selective NMR experiments.

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  • 21pCT-1 Eilenberger and London theories for field orientation dependence of flux line lattice form factors

    Ichioka M., Amano Y., Ishihara M., Nakai N., Machida K.

    Meeting Abstracts of the Physical Society of Japan   70   1652 - 1652   2015

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    DOI: 10.11316/jpsgaiyo.70.1.0_1652

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  • Eilenberger and London theories for transverse components of flux line lattice form factors in uniaxial superconductors

    Yuujirou Amano, Masahiro Ishihara, Masanori Ichioka, Noriyuki Nakai, Kazushige Machida

    PHYSICAL REVIEW B   90 ( 14 )   2014.10

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    We theoretically study the magnetic field orientation dependence of longitudinal and transverse flux line lattice form factors in uniaxial superconductors with anisotropy ratio corresponding to YBa2Cu3O7-delta. We discuss influences of the anisotropy ratio of coherence length and differences between the s-wave and the d(x2-y2)- wave pairings. The calculations are performed by two methods, the Eilenberger theory and the London theory comparatively, and we study the cutoff function of the extended London theory, which will be helpful in the analysis of the small angle neutron scattering in the vortex states.

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  • 9aPS-2 Vortex states in uniaxial superconductors when magnetic fields are tilted from the basal plane 2

    Amano Y., Ishihara M., Ichioka M., Machida K.

    Meeting abstracts of the Physical Society of Japan   69 ( 2 )   571 - 571   2014.8

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  • 10aBB-3 Quasi-classical Eilenberger theory for nuclear magnetic resonance in superconducting vortex core

    Tanaka K., Ichioka M., Nakai N., Machida K.

    Meeting abstracts of the Physical Society of Japan   69 ( 2 )   582 - 582   2014.8

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  • Knight shift spectrum in vortex states in s- and d-wave superconductors on the basis of Eilenberger theory

    Kenta K. Tanaka, Masanori Ichioka, Noriyuki Nakai, Kazushige Machida

    PHYSICAL REVIEW B   89 ( 17 )   2014.5

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    From the spatial structure of vortex lattice state calculated by Eilenberger theory, we study the resonance line shape of Knight shift of the paramagnetic moments in s- and d-wave superconductors, comparing with the Redfield pattern of the internal field distribution. We discuss the deviation from the temperature dependence of the Yosida function and the magnetic field dependence of the paramagnetic susceptibility. In addition to the calculation in the clean limit, influences of the impurity scattering are estimated in the Born limit and in the unitary limit. These results are helpful for the analysis of NMR experiments to know properties of the superconductors.

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  • 30aCA-9 Quasi-classical Eilenberger theory for nuclear magnetic resonance in superconducting vortex state

    Tanaka K., Ichioka M., Nakai N., Machida K.

    Meeting abstracts of the Physical Society of Japan   69 ( 1 )   813 - 813   2014.3

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  • 30aCM-10 空間反転対称性の欠如したパリティ混合超伝導体Li_2T_3B(T:Pd,Pt)の非磁性不純物効果の異常性(30aCM 超伝導物質,領域8(強相関係))

    包 桂芝, 江口 学, 小野 晶子, 俣野 和明, 稲田 佳彦, 前野 悦輝, 市岡 優典, 鄭 国慶

    日本物理学会講演概要集   69 ( 1 )   675 - 675   2014.3

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  • 30aCA-10 Flux line lattice form factor in uniaxial superconductors on the basis of Eilenberger theory

    Amano Y., Ishihara M., Ichioka M., Machida K.

    Meeting abstracts of the Physical Society of Japan   69 ( 1 )   813 - 813   2014.3

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  • Vortex States for Nearly B||ab in a Chiral p-Wave Superconductor (共著)

    M. Ichioka, M. Ishihara, Y. Amano, K. Machida

    JPS Conference Proceedings   3   015014-1-015022-6   2014

  • UPt3 as a Topological Crystalline Superconductor

    Yasumasa Tsutsumi, Masaki Ishikawa, Takuto Kawakami, Takeshi Mizushima, Masatoshi Sato, Masanori Ichioka, Kazushige Machida

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   82 ( 11 )   2013.11

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    We investigate the topological aspect of the spin-triplet f-wave superconductor UPt3 through microscopic calculations of edge-and vortex-bound states based on the quasiclassical Eilenberger and Bogoliubov-de Gennes theories. It is shown that a gapless and linear dispersion exists at the edge of the ab-plane. This forms a Majorana valley, protected by the mirror chiral symmetry. We also demonstrate that, with increasing magnetic field, vortex-bound quasiparticles undergo a topological phase transition from topologically trivial states in the double-core vortex to zero-energy states in the normal-core vortex. As long as the d-vector is locked into the ab-plane, the mirror symmetry holds the Majorana property of the zero-energy states, and thus UPt3 preserves topological crystalline superconductivity that is robust against the crystal field and spin-orbit interaction.

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  • Influence on superconductivity in the parity mixing superconductor Li2T3B(T:Pt,Pd) by non-magnetic impurity and defect doping

    G. Bao, Y. Inada, G. Eguchi, Y. Maeno, M. Ichioka, G. -Q. Zheng

    PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS   494   95 - 98   2013.11

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    Superconductors with noncentrosymmetric crystal structures such as Li2T3B(T:Pd,Pt) have been the focus of in-depth research with their parity mixing nature. In this study, we focused our research on non-magnetic impurity effect in Li2T3B(T:Pd,Pt). The nature of the pair breaking by non-magnetic impurity in the parity mixing superconducting state is still unclear. We prepared different quality samples of Li2Pd3B and Li2Pt3B by changing conditions in synthesizing, and sample qualities were estimated by residual resistivity. Spin singlet dominant superconductor Li2Pd3B exhibits the weak T-c suppression attributed by nonmagnetic impurity and defects, while H-c2 (0) value increased. This behavior is similar in ordinary s-wave superconductor. On the other hand, for the spin triplet dominant superconductor Li2Pt3B, it was suggested that the Cooper pair was broken and superconducting gap was decreased by non-magnetic impurities and defects. Li2Pt3B is similar to unconventional superconducting state. (C) 2013 Elsevier B.V. All rights reserved.

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  • Superconductivity in Ca-10(Ir4As8)(Fe2As2)(5) with Square-Planar Coordination of Iridium

    Kazutaka Kudo, Daisuke Mitsuoka, Masaya Takasuga, Yuki Sugiyama, Kento Sugawara, Naoyuki Katayama, Hiroshi Sawa, Hiroaki S. Kubo, Kenta Takamori, Masanori Ichioka, Tatsuo Fujii, Takashi Mizokawa, Minoru Nohara

    SCIENTIFIC REPORTS   3   2013.10

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    We report the unprecedented square-planar coordination of iridium in the iron iridium arsenide Ca-10(Ir4As8)(Fe2As2)(5). This material experiences superconductivity at 16 K. X-ray photoemission spectroscopy and first-principles band calculation suggest Ir(II) oxidation state, which yields electrically conductive Ir4As8 layers. Such metallic spacer layers are thought to enhance the interlayer coupling of Fe2As2, in which superconductivity emerges, thus offering a way to control the superconducting transition temperature.

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  • Vortex states in uniaxial superconductors when magnetic fields are tilted from the basal plane

    Amano Y., Ishihara M., Ichioka M., Machida K.

    Meeting abstracts of the Physical Society of Japan   68 ( 2 )   512 - 512   2013.8

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  • Quasi-classical theory for magnetic field dependence of Knight shift

    Tanaka K., Ichioka M.

    Meeting abstracts of the Physical Society of Japan   68 ( 2 )   713 - 713   2013.8

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  • Pauli paramagnetic effect in multi-band superconductivity

    Tsutsumi Y., Ichioka M., Machida K.

    Meeting abstracts of the Physical Society of Japan   68 ( 2 )   705 - 705   2013.8

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  • Vortex states in chiral p-wave superconductor for H//ab based on quasi-classical Eilenberger theory

    Ichioka M., Ishihara M., Amano Y., Machida K.

    Meeting abstracts of the Physical Society of Japan   68 ( 2 )   581 - 581   2013.8

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  • Anisotropy of the Superconducting State in Sr2RuO4

    C. Rastovski, C. D. Dewhurst, W. J. Gannon, D. C. Peets, H. Takatsu, Y. Maeno, M. Ichioka, K. Machida, M. R. Eskildsen

    PHYSICAL REVIEW LETTERS   111 ( 8 )   2013.8

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    Despite intense studies the exact nature of the order parameter in superconducting Sr2RuO4 remains unresolved. We have used small-angle neutron scattering to study the vortex lattice in Sr2RuO4 with the field applied close to the basal plane, taking advantage of the transverse magnetization. We measured the intrinsic superconducting anisotropy between the c axis and the Ru-O basal plane (similar to 60), which greatly exceeds the upper critical field anisotropy (similar to 20). Our result imposes significant constraints on possible models of triplet pairing in Sr2RuO4 and raises questions concerning the direction of the zero spin projection axis.

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  • 領域6,領域8,領域11「超伝導位相制御:量子化・ダイナミクスの物理と応用展開」(第68回年次大会シンポジウムの報告,学会報告)

    市岡 優典

    日本物理學會誌   68 ( 7 )   478 - 478   2013.7

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  • Transverse magnetic field and chiral-nonchiral transition in vortex states for nearly B parallel to ab in chiral p-wave superconductors

    Masahiro Ishihara, Yuujirou Amano, Masanori Ichioka, Kazushige Machida

    PHYSICAL REVIEW B   87 ( 22 )   2013.6

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    On the basis of Eilenberger theory, we study the vortex state when a magnetic field is applied nearly parallel to the ab plane in a chiral p-wave superconductor with a large anisotropy ratio of ab and c, as in Sr2RuO4. We quantitatively estimate the field dependence of the pair potential, magnetization, and flux-line lattice form factor, and study the transition from the chiral p_ state at low fields to the nonchiral p(y) state at high fields. Even for exactly parallel fields to the ab plane, transverse fields exist in the chiral state. The chiral-nonchiral transition disappears when the magnetic field orientation is tilted within 1 degrees from the ab plane. This may be a reason why the experimental detection of this transition is difficult.

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  • Rotation of Triangular Vortex Lattice in the Two-Band Superconductor MgB2

    Tomoya Hirano, Kenta Takamori, Masanori Ichioka, Kazushige Machida

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   82 ( 6 )   063708-1-063708-4   2013.6

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    To identify the contributions of the multiband nature and the anisotropy of a microscopic electronic structure to a macroscopic vortex lattice morphology, we develop a method based on the Eilenberger theory near Hc(2) combined with the first-principles band calculation to estimate the stable vortex lattice configuration. For a typical two-band superconductor MgB2, successive transitions of vortex lattice orientation that have been observed recently by small angle neutron scattering [Das et al.: Phys. Rev. Lett. 108 (2012) 167001] are explained by the characteristic fielddependence of two-band superconductivity and the competition of sixfold anisotropy between the sigma-and pi-bands. The reentrant transition at low temperature reflects the Fermi velocity anisotropy of the sigma-band.

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  • Surface Bound States and Spontaneous Current in Cyclic d-Wave Superconductors

    Masaki Ishikawa, Yasumasa Tsutsumi, Masanori Ichioka, Kazushige Machida

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   82 ( 4 )   2013.4

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    On the basis of Eilenberger theory, surface bound states and spontaneous current are studied in cyclic d-wave superconductors as a broken time-reversal symmetry of superconductivity in cubic lattice symmetry. We discuss how the spontaneous current and the electronic states depend on the orientation of the surface relative to the symmetry of superconductivity. The condition for topological Fermi arcs of zero-energy surface bound states to appear is identified in the complex pairing function of the cyclic d-wave.

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  • 29aXJ-2 The non-magnetic impurity effect in parity mixing superconductor Li_2T_3B(T=Pd,Pt)with nonoentyosymme tric crystal structures

    Bao G., Eguchi G., Inada Y., Ichioka M., Maeno Y., Zheng G-q.

    Meeting abstracts of the Physical Society of Japan   68 ( 1 )   688 - 688   2013.3

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  • 26aEN-1 Symposium "Phase control of superconductivity: Physics and application of the quantization and the dynamics" Purpose of the symposium

    Ichioka Masanori

    Meeting abstracts of the Physical Society of Japan   68 ( 1 )   856 - 856   2013.3

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  • 27pEM-5 Perpendicular components of flux line lattice form factor based on quasi-classical Eilenberger theory

    Ichioka M., Ishihara M., Amano Y., Machida K.

    Meeting abstracts of the Physical Society of Japan   68 ( 1 )   874 - 874   2013.3

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  • 27pEM-7 UPt_3 as a topological superconductor

    Tsutsumi Y., Ishikawa M., Kawakami T., Ichioka M., Machida K.

    Meeting abstracts of the Physical Society of Japan   68 ( 1 )   874 - 874   2013.3

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  • 26pXZE-9 Theoretical estimate of local electronic states in electric-field-induced surface superconductivity 2

    Mizohata Yousuke, Ichioka Masanori, Machida Kazushige

    Meeting abstracts of the Physical Society of Japan   68 ( 1 )   594 - 594   2013.3

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  • 26pXZE-9 Theoretical estimate of local electronic states in electric-field-induced surface superconductivity 2

    Mizohata Yousuke, Ichioka Masanori, Machida Kazushige

    Meeting abstracts of the Physical Society of Japan   68 ( 1 )   919 - 919   2013.3

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  • Multiple-gap structure in electric-field-induced surface superconductivity

    Yousuke Mizohata, Masanori Ichioka, Kazushige Machida

    PHYSICAL REVIEW B   87 ( 1 )   2013.1

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    Local superconducting gap structure is studied as a function of nanoscale depth in electric-field-induced surface superconductivity such as in SrTiO3. We examine solutions of the Bogoliubov-de Gennes equation in two limiting confinement potential cases of an electric field with and without screening effects. As unique properties different from bulk superconductivity, there appear in-gap states even for isotropic s-wave pairing, due to the multiple-gap structure of sub-band-dependent surface superconductivity. These determine the depth dependence of local superconductivity. DOI: 10.1103/PhysRevB.87.014505

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  • Field dependence of the specific heat in a heavy-fermion superconductor CeIrIn5

    Yuya Aoki, Shunichiro Kittaka, Toshiro Sakakibara, Akito Sakai, Satoru Nakatsuji, Yasumasa Tsutsumi, Masanori Ichioka, Kazushige Machida

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   81   2012.12

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    We investigated temperature, field, and field-orientation dependences of the specific heat of CeIrIn5. The upper critical field H-c2 was determined down to 80 mK from the specific heat measurements and exhibits a slight suppression at low temperatures. We revealed that the specific heat at 80 mK increases proportional to the square root of H up to nearly H-c2 for both H parallel to ab and H parallel to c, implying the presence of line nodes and a weak contribution of the Pauli paramagnetic pair-breaking effect. Furthermore, we revealed that the specific heat shows a fourfold oscillation under a rotating magnetic field in the ab plane. This result indicates that CeIrIn5 has fourfold symmetry around the c axis in its gap amplitude.

    DOI: 10.1143/JPSJS.81SB.SB014

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  • 18aAF-13 Rotation of triangular vortex lattice in a two-band superconductor MgB_2

    Takamori K., Hirano T., Ichioka M., Machida K.

    Meeting abstracts of the Physical Society of Japan   67 ( 2 )   720 - 720   2012.8

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  • 20pFE-5 Theoretical estimate of local electronic states in electric-field-induced surface superconductivity

    Mizohata Yousuke, Ichioka Masanori, Machida Kazushige

    Meeting abstracts of the Physical Society of Japan   67 ( 2 )   795 - 795   2012.8

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  • 20pFE-5 Theoretical estimate of local electronic states in electric-field-induced surface superconductivity

    Mizohata Yousuke, Ichioka Masanori, Machida Kazushige

    Meeting abstracts of the Physical Society of Japan   67 ( 2 )   540 - 540   2012.8

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  • Odd-frequency Cooper-pair amplitude around a vortex core in a chiral p-wave superconductor in the quantum limit

    Takeshi Daino, Masanori Ichioka, Takeshi Mizushima, Yukio Tanaka

    PHYSICAL REVIEW B   86 ( 6 )   2012.8

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    Solving the Bogoliubov-de Gennes equation, we study the spatial structure of odd-frequency s-wave Cooper-pair amplitudes at each quantized energy level of vortex bound states in chiral p-wave superconductors. For zero-energy Majorana states, the odd-frequency s-wave pair amplitude has the same spatial structure as that of the local density of states even in an atomic length scale. This relation also holds in finite energy bound states for single vortex winding antiparallel to the chirality, but not for parallel vortex winding. The double winding vortex case is also studied.

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  • 25aBC-9 Odd Frequency Coopar Pairing around a Vortex Core of Chiral p-Wave Superconductors in Quantum Limit

    Mizushima T., Daino T., Ichioka M., Tanaka Y.

    Meeting abstracts of the Physical Society of Japan   67 ( 1 )   839 - 839   2012.3

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  • 27aBC-6 Edge state and edge current for superfluid helium-3

    Tsutsumi Y., Mizushima T., Ichioka M., Machida K.

    Meeting abstracts of the Physical Society of Japan   67 ( 1 )   854 - 854   2012.3

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  • 24pBC-4 Vortex state near H_<c1> in two-band superconductors

    Ichioka Masanori, Suzuki kenta, Machida Kazushige

    Meeting abstracts of the Physical Society of Japan   67 ( 1 )   835 - 835   2012.3

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  • Superconducting gap structure of CeIrIn 5 from field-angle-resolved measurements of its specific heat

    Shunichiro Kittaka, Yuya Aoki, Toshiro Sakakibara, Akito Sakai, Satoru Nakatsuji, Yasumasa Tsutsumi, Masanori Ichioka, Kazushige Machida

    Physical Review B - Condensed Matter and Materials Physics   85   2012.2

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    In order to identify the gap structure of CeIrIn 5 , we measured field-angle-resolved specific heat C(φ) by conically rotating the magnetic field H around the c axis at low temperatures down to 80 mK. We revealed that C(φ) exhibits a fourfold angular oscillation, whose amplitude decreases monotonically by tilting H out of the ab plane. Detailed microscopic calculations based on the quasiclassical Eilenberger equation confirm that the observed features are uniquely explained by assuming the d x2-y2 -wave gap. These results strongly indicate that CeIrIn 5 is a d x2-y2 -wave superconductor and suggest the universal pairing mechanism in CeMIn 5 (M=Co, Rh, and Ir). © 2012 American Physical Society.

    DOI: 10.1103/PhysRevB.85.060505

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  • Superconducting gap structure of CeIrIn5 from field-angle-resolved measurements of its specific heat

    Shunichiro Kittaka, Yuya Aoki, Toshiro Sakakibara, Akito Sakai, Satoru Nakatsuji, Yasumasa Tsutsumi, Masanori Ichioka, Kazushige Machida

    PHYSICAL REVIEW B   85 ( 6 )   2012.2

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    In order to identify the gap structure of CeIrIn5, we measured field-angle-resolved specific heat C(phi) by conically rotating the magnetic field H around the c axis at low temperatures down to 80 mK. We revealed that C(phi) exhibits a fourfold angular oscillation, whose amplitude decreases monotonically by tilting H out of the ab plane. Detailed microscopic calculations based on the quasiclassical Eilenberger equation confirm that the observed features are uniquely explained by assuming the d(x2-y2)-wave gap. These results strongly indicate that CeIrIn5 is a d(x2-y2)-wave superconductor and suggest the universal pairing mechanism in CeMIn5 (M = Co, Rh, and Ir).

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  • On Intrinsic Angular Momentum due to Edge Mass Current for Superfluid He-3 A-Phase

    Y. Tsutsumi, T. Mizushima, M. Ichioka, K. Machida

    26TH INTERNATIONAL CONFERENCE ON LOW TEMPERATURE PHYSICS (LT26), PTS 1-5   400   2012

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    In the superfluid He-3 A-phase, the edge mass current which accompanies surface Andreev bound states flows due to topological features. We discuss the relation between the angular momentum by the edge mass current and the macroscopic intrinsic angular momentum = N (h) over bar /2 by the Cooper pairs with aligned angular momenta, based on the quasi-classical theory. At the low temperature limit, half of the edge mass current from the bound state is canceled by that from the continuum state. Then, the magnitude of the total angular momentum is L = N (h) over bar /2 which corresponds to the macroscopic intrinsic angular momentum of N particles. The net angular momentum decreases monotonously toward zero at the transition temperature. However, that is larger than the macroscopic intrinsic angular momentum expected from the same behavior of the superfluid density in middle temperatures.

    DOI: 10.1088/1742-6596/400/1/012076

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  • Majorana Fermions Bound at Vortices and Surface of Superfluid He-3

    T. Mizushima, T. Kawakami, Y. Tsutsumi, M. Ichioka, K. Machida

    26TH INTERNATIONAL CONFERENCE ON LOW TEMPERATURE PHYSICS (LT26), PTS 1-5   400   2012

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    We investigate the Majorana fermions bound at vortices and specular surface of superfluid He-3 A- and B-phases. It is demonstrated that the statistics of the integer vortex which is competitive to the half-quantum vortex is sensitive to the orientation of the magnetic field. We also discuss the surface Andreev bound state in the B-phase, which is expected to behave as Majorana fermions at the zero field limit. Based on the quasiclassical and Bogoliubov-de Gennes theories, we clarify that in the presence of the magnetic field parallel to the surface, the stable configuration of the (n) over cap -vector, which reflects the spin-orbit symmetry breaking, traces the point at which the surface state has the maximum gap.

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  • Vortex States of Chiral p-wave Superconductors

    M. Ichioka, K. Machida, J. A. Sauls

    26TH INTERNATIONAL CONFERENCE ON LOW TEMPERATURE PHYSICS (LT26), PTS 1-5   400   2012

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    In chiral p-wave superconductors a flux lattice of doubly quantized vortices is shown to be energetically stable for fields H-c1 < H-FL < H < H-c2, while at low fields a lattice of singly quantized vortices is stable. Here we report self-consistent calculations by Eilenberger theory for spatial structures of the pair potential and current density for vortex states of single- and double-winding vortices in chiral p-wave superconductors with a cylindrical Fermi surface.

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  • Field Evolution of the Fulde-Ferrell-Larkin-Ovchinnikov State in a Superconductor with Strong Pauli Effects

    Kenta M. Suzuki, Yasumasa Tsutsumi, Noriyuki Nakai, Masanori Ichioka, Kazushige Machida

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   80 ( 12 )   2011.12

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    The Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) phase in the vortex lattice state is quantitatively studied using the self-consistent Eilenberger theory in three-dimensional (3D) space. We estimate free energy to determine the FFLO phase diagram in the H-T plane and stable FFLO wave number in the isotropic system with the 3D Fermi sphere and s-wave pairing. To facilitate the experimental identification of the FFLO state, we investigate the field evolution of NMR spectra and flux line lattice form factors obtained in neutron scattering in the FFLO vortex states. Possible applications of our results to experimental data on CeCoIn5 are mentioned.

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  • Origin of Spontaneous Broken Mirror Symmetry of Vortex Lattices in Nb

    Hiroki M. Adachi, Masaki Ishikawa, Tomoya Hirano, Masanori Ichioka, Kazushige Machida

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   80 ( 11 )   2011.11

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    Combining the microscopic Eilenberger theory with the first-principles band calculation, we investigate the stable flux line lattice (FLL) for a field applied to the fourfold axis, i.e., H parallel to [001] in cubic Nb. The observed FLL transformation along H-c2 is almost perfectly explained without using adjustable parameter, including the tilted square, scalene triangle with broken mirror symmetry, and isosceles triangle lattices upon increasing T. We construct a minimum Fermi surface model to understand such morphologies, particularly the stability of the scalene triangle lattice attributed to the lack of mirror symmetry about the Fermi velocity maximum direction in k-space.

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  • Multiple superconducting gap and anisotropic spin fluctuations in iron arsenides: Comparison with nickel analog

    Z. Li, S. Kawasaki, T. Oka, T. Tabuchi, Y. Ooe, M. Ichioka, Z. A. Ren, Z. X. Zhao, J. L. Luo, N. L. Wang, X. C. Wang, Q. Q. Liu, C. Q. Jin, C. T. Lin, Guo-qing Zheng

    JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS   72 ( 5 )   492 - 496   2011.5

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    We present extensive (75)As NMR and NQR data on the superconducting arsenides PrFeAs(0.89)F(0.11) (T(c) = 45 K), LaFeAsO(0.92)F(0.08) (T(c) = 27 K), LiFeAs (T(c) = 17 K) and Ba(0.72)K(0.28)Fe(2)As(2) (T(c) = 31.5 K) single crystal, and compare with the nickel analog LaNiAsO(0.9)F(0.1) (T(c) = 4.0 K). In contrast to LaNiAsO(0.9)F(0.1) where the superconducting gap is shown to be isotropic, the spin lattice relaxation rate 1/T(1) in the Fe-arsenides decreases below T(c) with no coherence peak and shows a step-wise variation at low temperatures. The Knight shift decreases below T(c) and shows a step-wise T variation as well. These results indicate spin-singlet superconductivity with multiple gaps in the Fe-arsenides. The Fe antiferromagnetic spin fluctuations are anisotropic and weaker compared to underdoped copper-oxides or cobalt-oxide superconductors, while there is no significant electron correlations in LaNiAsO(0.9)F(0.1). We will discuss the implications of these results and highlight the importance of the Fermi surface topology. Crown Copyright (C) 2010 Published by Elsevier Ltd. All rights reserved.

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  • Theory of an inherent spin-density-wave instability due to vortices in superconductors with strong Pauli effects

    Kenta M. Suzuki, Masanori Ichioka, Kazushige Machida

    PHYSICAL REVIEW B   83 ( 14 )   2011.4

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    A spin-density-wave (SDW) instability mechanism enhanced by vortices under fields is proposed to explain the high field and low-temperature phase in CeCoIn5. In the vortex state strong Pauli effect and nodal gap conspire to enhance the momentum-resolved density of states over the normal state value exclusively along the nodal direction, providing a favorable nesting condition for SDW with Q = (2k(F), 2k(F), 0.5) only at high fields (H). We can consistently understand observed mysteries of the field-induced SDW confined below H-c2, such as facts that Q is directed to the nodal direction independent of H, SDW diminishes under tilting field from the ab plane, and the SDW transition line in (H, T) has a positive slope.

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  • Majorana surface states of superfluid He-3 A and B phases in a slab

    Y. Tsutsumi, M. Ichioka, K. Machida

    PHYSICAL REVIEW B   83 ( 9 )   2011.3

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    Motivated by experiments on the superfluid He-3 confined in a thin slab, we design a concrete experimental setup for observing the Majorana surface states. We solve the quasiclassical Eilenberger equation, which is quantitatively reliable, to evaluate several quantities, such as local density of states (LDOS), mass current for the A phase, and spin current for the B phase. In connection with realistic slab samples, we consider the upper and lower surfaces and the side edges including the corners with several thicknesses. Consequently, the influence on the Majorana zero modes from the spatial variation of the l vector for the A phase in thick slabs and the energy splitting of the zero-energy quasiparticles for the B phase confined in thin slabs are demonstrated. The corner of slabs in the B phase is accompanied by the unique zero-energy LDOS of corner modes. On the basis of the quantitative calculation, we propose several feasible and verifiable experiments to check the existence of the Majorana surface states, such as the measurement of specific heat, edge current, and anisotropic spin susceptibility.

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  • Majorana Edge Modes of Superfluid He-3 A- and B-Phases

    Y. Tsutsumi, T. Mizushima, M. Ichioka, K. Machida

    JOURNAL OF LOW TEMPERATURE PHYSICS   162 ( 3-4 )   196 - 203   2011.2

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    Motivated by a recent experiment on the superfluid He-3 confined in a thin slab, we discuss the Majorana edge modes under the experimental situation. We solve the quasi-classical Eilenberger equation, which is quantitatively reliable, to evaluate several observables, such as local density of states, mass current for the A-phase, and spin current for the B-phase. On the basis of the quantitative calculation, we propose several experiments to check the existence of the Majorana modes.

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  • Lower Critical Field H-c1(T) and Pairing Symmetry Based on Eilenberger Theory

    Takanobu Akiyama, Masanori Ichioka, Kazushige Machida

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   80 ( 1 )   2011.1

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  • Vortex lattice transformation in d-wave superconductors with Pauli paramagnetic effect

    Kenta M. Suzuki, Masanori Ichioka, Kazushige Machida

    PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS   470   S564 - S565   2010.12

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    By self-consistently solving the Eilenberger equations in a vortex state, we quantitatively evaluate the free energy for various lattice configurations of the d-wave superconductor under applied magnetic fields along to the c-axis, and discuss the dependence of stable configuration on the paramagnetic effect. By the paramagnetic effect, though the distribution of zero energy local density of states does not extend to the nodal direction above the middle fields, it still has good connection with vortex cores at the nodal directions. Then it makes square vortex lattice stable. We show that there is a first-order orientational transition before rocking into the square vortex lattice at low fields. (C) 2009 Elsevier B.V. All rights reserved.

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  • As-75 NMR studies of superconducting Ba0.72K0.28Fe2As2

    Z. Li, K. Matano, D. L. Sun, G. L. Sun, C. T. Lin, M. Ichioka, G. -Q. Zheng

    PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS   470   S495 - S496   2010.12

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    We have performed As-75 nuclear magnetic resonance measurements on a single crystal of the hole-doped superconductor Ba0.72K0.28Fe2As2 (T-c = 31.5 K). The spin-lattice relaxation rate 1/T-1 decreases below T-c with no coherence peak and shows a step-wise variation at low temperatures, which is indicative of multiple superconducting gaps. In the normal state, we find that Fe antiferromagnetic spin fluctuations are anisotropic. (C) 2009 Elsevier B.V. All rights reserved.

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  • Theory of superconducting symmetry in vortex lattice state

    Takehito Yokoyama, Masanori Ichioka, Yukio Tanaka

    PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS   470   S886 - S887   2010.12

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    We investigate symmetry of pairing correlation in vortex lattice state, and explain the electronic structure in this state in terms of pairing symmetry. We find that only odd-frequency pairing is present at the core centers, while at the midpoint of the vortex lines, only even-frequency pairing exists. Thus, the odd- and even-frequency pairings also form the lattice in the vortex lattice state. (C) 2009 Elsevier B.V. All rights reserved.

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  • Majorana Edge Modes of Superfluid He-3 A-Phase in a Slab

    Yasumasa Tsutsumi, Takeshi Mizushima, Masanori Ichioka, Kazushige Machida

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   79 ( 11 )   2010.11

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    Motivated by a recent experiment on the superfluid He-3 A-phase with a chiral p-wave pairing confined in a thin slab, we propose designing a concrete experimental setup for observing the Majorana edge modes that appear around the circumference edge region. We solve the quasi-classical Eilenberger equation, which is quantitatively reliable, to evaluate several observables. To derive the property inherent to the Majorana edge state, the full quantum mechanical Bogoliubov-de Gennes equation is solved in this setting. On the basis of the results obtained, we perform decisive experiments to check the Majorana nature.

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  • Theory of pairing symmetry in the vortex states

    Takehito Yokoyama, Masanori Ichioka, Yukio Tanaka, Alexander Golubov

    PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS   470 ( 19 )   766 - 770   2010.10

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    We investigate pairing symmetry in an Abrikosov vortex and vortex lattice. It is shown that the Cooper pair wave function at the center of an Abrikosov vortex with vorticity m has a different parity with respect to frequency from that in the bulk if m is an odd number, while it has the same parity if m is an even number. As a result, in a conventional vortex with m = 1, the local density of states at the Fermi energy has a maximum (minimum) at the center of the vortex core in an even (odd)-frequency superconductor. In the vortex lattice of s-wave superconductor, we find that only odd-frequency pairing is present at the core centers, while at the midpoint of the vortex lines, only even-frequency pairing exists. Thus, the odd and even-frequency pairings also form the lattice in the vortex lattice state. We also propose a scanning tunneling microscope experiment using a superconducting tip to explore odd-frequency superconductivity. (C) 2010 Elsevier B.V. All rights reserved.

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  • Skyrmion lattice and intrinsic angular momentum effect in the A phase of superfluid He-3 under rotation

    Masanori Ichioka, Takeshi Mizushima, Kazushige Machida

    PHYSICAL REVIEW B   82 ( 9 )   2010.9

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    As an example of the skyrmion lattice, the structure of Mermin-Ho vortex lattice in superfluids He-3 is studied by self-consistent Eilenberger theory and by Bogoliubov-de Gennes theory. We identify how the intrinsic orbital angular momentum 1 of p-wave Cooper pairs contributes to spatial structures of the pair potential, current flow, and quasiparticle states. There are two types of vortices depending on the 1 direction relative to rotation. Only one of them has zero-energy bound states appearing even in coreless vortices due to intrinsic topological reasons.

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  • Vortex State and Field-Angle Resolved Specific Heat Oscillation for H parallel to ab in d-Wave Superconductors

    Masayuki Hiragi, Kenta M. Suzuki, Masanori Ichioka, Kazushige Machida

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   79 ( 9 )   2010.9

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    When magnetic field is applied parallel to the ab-plane in d(x2-y2)-wave superconductors, the transition of a stable vortex lattice structure, the spatial structure of local density of states, and the specific heat oscillation induced by rotation of the magnetic field orientation are investigated by quantitative calculations based on the self-consistent Eilenberger theory. We estimate how the vortex state changes depending on the relative angle between the node direction of the superconducting gap and magnetic field orientation. To reproduce the sign change of specific heat oscillation observed in CeCoIn5, our study is perfomed by including a strong paramagnetic effect. The quantitative theoretical calculations give decisive information to analyze the experimental data on the field-angle dependence, and establish the angle-resolved specific heat experiment as a spectroscopic means to identify the node position of the superconducting gap.

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  • As-75 NQR and NMR Studies of Superconductivity and Electron Correlations in Iron Arsenide LiFeAs

    Zheng Li, Yosuke Ooe, Xian-Cheng Wang, Qing-Qing Liu, Chang-Qing Jin, Masanori Ichioka, Guo-qing Zheng

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   79 ( 8 )   2010.8

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    We report the As-75-NQR and NMR studies on the iron arsenide superconductor LiFeAs with T-c similar to 17 K. The spin lattice relaxation rate, 1/T-1, decreases below T-c without a coherence peak, and can be fitted by gaps with s(+/-)-wave symmetry in the presence of impurity scattering. In the normal state, both 1/T1T and the Knight shift decrease with decreasing temperature but become constant below T <= 50 K. Estimate of the Korringa ratio shows that the spin correlations are weaker than those in other families of iron arsenides, which may account for the lower T-c in this material.

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  • Theory of Pairing Symmetry in Fulde-Ferrell-Larkin-Ovchinnikov Vortex State and Vortex Lattice

    Takehito Yokoyama, Masanori Ichioka, Yukio Tanaka

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   79 ( 3 )   2010.3

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    We investigate the pairing symmetry of induced superconductivity in two systems, namely, (i) the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) vortex state and (ii) vortex lattice state without FFLO modulation, and explain the electronic structure in these states in terms of pairing symmetry. We analytically show that, at the intersection point of the FFLO nodal plane and vortex line, only even-frequency pairing is present if the Zeeman splitting is negligible. With increasing Zeeman splitting, odd-frequency pairing emerges at such a point. In the vortex lattice, we find that only odd-frequency pairing is present at core centers, while at the midpoint of vortex lines, only even-frequency pairing exists.

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  • Textures and Exotic Vortices in Neutral Fermion Superfluids

    K. Machida, Y. Tsutsumi, T. Kawakami, H. M. Adachi, J. A. M. Huhtamaki, T. Mizushima, M. Ichioka

    JOURNAL OF LOW TEMPERATURE PHYSICS   158 ( 3-4 )   377 - 383   2010.2

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    There has been intense interest in various Fermion superfluids in neutral atom liquids and gases, including chiral p-wave pairing in He-3-A phase and Feshbach-resonanced Li-6 atom gases and d-wave pairing in atom gases. It is particularly interesting to find exotic vortices and associated low-lying Fermionic excitations under rotation. Here we report on our efforts of those topics: (1) Majorana Fermion in chiral superfluids near a p-wave Feshbach resonance. (2) Possible half-quantum vortices in p-wave superfluids of trapped Fermion atom gases. (3) Stability of a half-quantum vortex in rotating superfluid He-3-A between parallel plates. (4) Majorana bound state in rotating superfluid He-3-A between parallel plates. (5) Non-Abelian Fractional vortex in d-wave Feshbach resonance superfluids. We will summarize some of those works in a coherent manner in order to bridge the understanding between cold atom community and superfluid He-3 community by stressing the importance of cross fertilization between them.

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  • Sign Reversal of Field-Angle Resolved Heat Capacity Oscillations in a Heavy Fermion Superconductor CeCoIn5 and dx2-y2 Pairing Symmetry

    K. An, T. Sakakibara, R. Settai, Y. Onuki, M. Hiragi, M. Ichioka, K. Machida

    PHYSICAL REVIEW LETTERS   104 ( 3 )   2010.1

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    To identify the superconducting gap symmetry in CeCoIn5 (T-c = 2.3 K), we measured the angle-resolved specific heat (C-phi) in a field rotated around the c axis down to a very low temperature, 0.05T(c), and made detailed theoretical calculations. In a field of 1 T, a sign reversal of the fourfold angular oscillation in C-phi was observed at T similar or equal to 0.1T(c) upon entering a quasiclassical regime where the maximum of C-phi corresponds to the antinodal direction, coinciding with the angle-resolved density of states (ADOS) calculation. The C-phi behavior, which exhibits minima along the [110] directions, unambiguously allows us to conclude d(x2-y2) symmetry of this system. The ADOS-quasiclassical region is confined to a narrow T and H domain within T/T-c similar to 0.1 and 1.5 T (0.13H(c2)).

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  • Generic First-Order Orientation Transition of Vortex Lattices in Type II Superconductors

    Kenta M. Suzuki, Kenji Inoue, Predrag Miranovic, Masanori Ichioka, Kazushige Machida

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   79 ( 1 )   2010.1

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    The first-order transition of vortex lattices (VLs) observed in various superconductors with fourfold symmetry is explained microscopically by quasi-classical Eilenberger theory combined with nonlocal London theory. This transition is intrinsic in the generic successive VL phase transition due to either gap anisotropy or Fermi velocity anisotropy. This is also suggested by the electronic states around vortices. Ultimately, the origin of this phenomenon is attributed to somewhat hidden frustrations of a spontaneous symmetry-broken hexagonal VL in the underlying fourfold crystalline symmetry.

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  • Anisotropic spin fluctuations and multiple superconducting gaps in hole-doped Ba0.72K0.28Fe2As2: NMR in a single crystal

    K. Matano, Z. Li, G. L. Sun, D. L. Sun, C. T. Lin, M. Ichioka, Guo-Qing Zheng

    EPL   87 ( 2 )   27012, 1-6   2009.7

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    We report the As-75-NMR study on a single crystal of the hole-doped iron-pnictide superconductor Ba0.72K0.28Fe2As2 (T-c = 31.5 K). We find that the Fe antiferromagnetic spin fluctuations are anisotropic and are weaker compared to underdoped copper-oxides or cobalt-oxide superconductors. The spin lattice relaxation rate 1/T-1 decreases below T-c with no coherence peak and shows a stepwise variation at low temperatures, which is indicative of multiple superconducting gaps, as in the electron-doped Pr(La) FeAsO1-xFx. Furthermore, no evidence was obtained for a microscopic coexistence of a long-range magnetic order and superconductivity. Copyright (C) EPLA, 2009

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  • p波超流動体の量子渦に潜むマヨラナ型準粒子

    水島健, 市岡 優典, 町田 一成

    日本物理学会誌   64 ( 11 )   836 - 840   2009

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  • Singular and Non-singular Vortices and Their Excitation Spectra of Neutral Fermi Superfluids in Restricted Geometries

    K. Machida, Y. Tsutsumi, T. Kawakami, T. Mizushima, M. Ichioka, M. Takahashi

    25TH INTERNATIONAL CONFERENCE ON LOW TEMPERATURE PHYSICS (LT25), PART 3   150 ( 3 )   032049, 1-4   2009

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    We study stable vortices and their bound excitation spectra in superfluid (3)He-A phase under restricted geometries. By choosing appropriate geometry we can control the (l) over right arrow -vector and (d) over right arrow -vector of the A phase order parameter (OP), making it possible to select a particular vortex among a variety of singular or non-singular vortices. This tunability through the boundary condition and external field is demonstrated to be useful. Here we take up two examples of the restricted geometries under rotation: A narrow cylinder whose radius is 50 mu m under field parallel to the rotation axis and thin film configuration sandwiched by parallel plates whose gap is an order of mu m or less. We examine the ongoing experiment by rotating cryostat at ISSP, University of Tokyo, reporting on new vortex state for a cylinder in a slow rotation speed region near T(c). For parallel plates in a field parallel to the film surface we analyze the conditions under which singular vortex is stable. This study allows us to examine experimental realization of so-called Majorana zero energy state bound in a core in (3)He-A chiral phase.

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  • Flux line lattice form factor and paramagnetic effects in type II superconductors

    Masanori Ichioka, Kazushige Machida

    25TH INTERNATIONAL CONFERENCE ON LOW TEMPERATURE PHYSICS (LT25), PART 5   150 ( 5 )   052074, 1-4   2009

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    Based on the quasiclassical Eilenberger theory, we investigate the vortex structure in type II superconductors with strong Pauli-paramagnetic contributions due to the Zeeman effect. We quantitatively study how the paramagnetic effect suppresses the superconductivity, and evaluate the flux line lattice (FLL) form factor from the calculated internal field distribution both in the s-wave and d-wave pairings. When the paramagnetic effects are strong, the intensity of the FLL form factor increases toward H(c2) as a function of an applied field, instead of exponential decay. This anomalous field dependence is due to the induced paramagnetic moments around the vortex core. We discuss the anomalous field-dependence of the FLL form factor observed by the small angle neutron scattering in CeCoIn(5).

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  • Majorana Fermions in Quantized Vortices of p-Wave Superfluids

    Takeshi Mizushima, Masanori Ichioka, Kazushige Machida

    Butsuri   64   836 - 840   2009

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  • Role of the Majorana Fermion and the Edge Mode in Chiral Superfluidity near a p-Wave Feshbach Resonance

    T. Mizushima, M. Ichioka, K. Machida

    PHYSICAL REVIEW LETTERS   101 ( 15 )   150409 1-4   2008.10

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    The visualization of chiral p-wave superfluidity in Fermi gases near p-wave Feshbach resonances is theoretically examined. It is proposed that the superfluidity becomes detectable in the entire BCS-BEC regimes through (i) vortex visualization by the density depletion inside the vortex core and (ii) intrinsic angular momentum in vortex-free states. It is revealed that both (i) and (ii) are closely connected with the Majorana zero energy mode of the vortex core and the edge mode, which survive until the strong coupling BCS regime is approached from the weak coupling limit and vanish in the Bose-Einstein condensation regime.

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  • Majorana bound state in rotating superfluid (3)He-A between parallel plates

    Y. Tsutsumi, T. Kawakami, T. Mizushima, M. Ichioka, K. Machida

    PHYSICAL REVIEW LETTERS   101 ( 13 )   135302 1-4   2008.9

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    A concrete and experimentally feasible example for testing the putative Majorana zero-energy state bound in a vortex is theoretically proposed for a parallel plate geometry of superfluid (3)He-A phase. We examine the experimental setup in connection with ongoing rotating cryostat experiments. The theoretical analysis is based on the well-established Ginzburg-Landau functional, supplemented by microscopic calculations of the Bogoliubov-de Gennes equation, both of which allow the precise location of the parameter regions of the Majorana state to be found in realistic situations.

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  • Magnetization profile and core-level spectroscopy in a multiply quantized vortex of imbalanced Fermi superfluids Reviewed

    K. M. Suzuki, T. Mizushima, M. Ichioka, K. Machida

    Physical Review A - Atomic, Molecular, and Optical Physics   77 ( 6 )   2008.6

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    The core structure of multiply quantized vortices is theoretically investigated in a fermionic superfluid near Feshbach resonance. Under population imbalance in two hyperfine spin states, the vortex core is filled in by the "paramagnetic moment." Here, we find the spatial oscillation of the magnetization inside the core sensitively due to the topological structure of the pairing field, in the range from the weak-coupling regime to the unitary limit. This magnetization inside the giant core reveals the winding number of the vortex and directly results from the low-lying quasiparticle states bound inside the core. It is therefore proposed that the density profile experiment using phase contrast imaging can provide the spectroscopy of novel core level structures in giant vortices. To help understand these outcomes, we also derive an analytic solution for the low-lying quasiparticle states inside the core of a multiply quantized vortex. © 2008 The American Physical Society.

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  • Magnetic field dependence of low-temperature specific heat in Sr(2)RuO(4)

    K. Machida, M. Ichioka

    PHYSICAL REVIEW B   77 ( 18 )   184515 1   2008.5

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    The magnetic field (H) dependence of the Sommerfeld coefficient gamma(H) of the low-temperature specific heat in Sr(2)RuO(4) is analyzed by numerically solving the microscopic Eilenberger equation. By taking account of the strong Pauli-paramagnetic effect, we find that gamma(H) exhibits a systematic change from a concave function root H to a convex function H(alpha)(alpha&gt;1) at high fields when the orientation of the magnetic field is varied, explaining experimental results. The magnetization is found to be consistent with this behavior. This implies either singlet pairing or triplet pairing with the d vector locked in the basal plane. Based on this conclusion, we explain other properties of this compound.

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  • Field-angle-dependent specific heat measurements and gap determination of a heavy fermion superconductor URu(2)Si(2)

    K. Yano, T. Sakakibara, T. Tayama, M. Yokoyama, H. Amitsuka, Y. Homma, P. Miranovic, M. Ichioka, Y. Tsutsumi, K. Machida

    PHYSICAL REVIEW LETTERS   100 ( 1 )   017004 1-4   2008.1

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    To identify the superconducting gap structure in URu(2)Si(2), we perform field-angle-dependent specific heat measurements for the two principal orientations in addition to field rotations, and a theoretical analysis based on microscopic calculations. The Sommerfeld coefficient gamma(H)&apos;s in the mixed state exhibit a distinctly different field dependence. This comes from point nodes and the substantial Pauli paramagnetic effect of URu(2)Si(2). These two features combined give rise to a consistent picture of superconducting properties, including a possible first order transition of H(c2) at low temperatures.

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  • LITTLE-PARKS OSCILLATIONS IN CHIRAL p-WAVE SUPERCONDUCTING RINGS

    M. Takigawa, Y. Asano, M. Ichioka

    CONTROLLABLE QUANTUM STATES: MESOSCOPIC SUPERCONDUCTIVITY AND SPRINTRONICS   155 - +   2008

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    Oscillations of critical temperature T-c of superconducting rings under the applied magnetic field are studied based on the time-dependent Ginzburg-Landau theory. We analyze the Little-Parks oscillations in s-wave and chiral p-wave superconductors. In s-wave superconductor, we confirm clear oscillations in T-c. When phase winding numbers around a bole change, T-c takes local minimum. Period of oscillation behaviors depends oil a shape of rings. The conventional Little-Parks oscillations do not appear in chiral p-wave superconductor because of the unusual flux penetration in superconducting ring.

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  • Electronic thermal conductivity in a superconducting vortex state

    H. Adachi, P. Miranovic, M. Ichioka, K. Machida

    PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS   463   36 - 39   2007.10

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    The longitudinal component of the electronic thermal conductivity kappa(xx) in a superconducting vortex state is calculated as a function of magnetic field B. Calculations are performed by taking account of the spatial dependence of normal Green's function g, which was neglected in the previous studies using the Brandt-Pesch-Tewordt method. We discuss the possibility of using kappa(xx)(B) as a probe of the pair potential symmetry. (C) 2007 Elsevier B.V. All rights reserved.

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  • Pauli paramagnetic effects on vortices in superconducting TmNi2B2C

    L. DeBeer-Schmitt, M. R. Eskildsen, M. Ichioka, K. Machida, N. Jenkins, C. D. Dewhurst, A. B. Abrahamsen, S. L. Bud'ko, P. C. Canfield

    PHYSICAL REVIEW LETTERS   99 ( 16 )   167001 1-4   2007.10

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    The magnetic field distribution around the vortices in TmNi2B2C in the paramagnetic phase was studied experimentally as well as theoretically. The vortex form factor, measured by small-angle neutron scattering, is found to be field independent up to 0.6H(c2) followed by a sharp decrease at higher fields. The data are fitted well by solutions to the Eilenberger equations when paramagnetic effects due to the exchange interaction with the localized 4f Tm moments are included. The induced paramagnetic moments around the vortex cores act to maintain the field contrast probed by the form factor.

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  • Imbalanced superfluid phase of a trapped fermi gas in the BCS-BEC crossover regime

    Takeshi Mizushima, Masanori Ichioka, Kazushige Machida

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   76 ( 10 )   104006 1-15   2007.10

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    We theoretically investigate the ground state of trapped neutral fermions with population imbalance in the BCS-BEC crossover regime. On the basis of the single-channel Hamiltonian, we perform full numerical calculations of the Bogoliubov-de Gennes equation coupled with the regularized gap and number equations. The zero-temperature phase diagram in the crossover regime is presented, where the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) pairing state governs the weak-coupling BCS region of a resonance. It is found that the FFLO oscillation vanishes in the BEC side, in which the system under population imbalance turns into a phase separation (PS) between locally binding superfluid and fully polarized spin domains. We also demonstrate numerical calculations with a large particle number O(10(5)), comparable to that observed in recent experiments. The resulting density profile on a resonance yields the PS, which is in good agreement with the recent experiments, while the FFLO modulation exists in the pairing field. It is also proposed that the most favorable location for the detection of the FFLO oscillation is in the vicinity of the critical population imbalance in the weak coupling BCS regime, where the oscillation periodicity becomes much larger than the interparticle spacing. Finally, we analyze the radio-frequency (RF) spectroscopy in the imbalanced system. The clear difference in the RF spectroscopy between BCS and BEC sides reveals the structure of the pairing field and local "magnetization".

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  • カイラルp波超伝導でのリトル・パークス振動

    市岡優典, 町田一成, 石棉元, 瀧川光明, 瀧川光明, 浅野泰寛

    日本物理学会講演概要集   62 ( 2 )   587   2007.8

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  • Vortex states in superconductors with strong Pauli-paramagnetic effect

    Masanori Ichioka, Kazushige Machida

    PHYSICAL REVIEW B   76 ( 6 )   064502 1-7   2007.8

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    Using quasiclassical theory, we analyze the vortex structure of strong-paramagnetic superconductors. There, induced paramagnetic moments are accumulated exclusively around the vortex core. We quantitatively evaluate the significant paramagnetic effect in the H dependence of various quantities, such as low temperature specific heat, Knight shift, magnetization, and the flux line lattice (FLL) form factor. The anomalous H dependence of the FLL form factor observed by the small angle neutron scattering in CeCoIn5 is attributable to the large paramagnetic contribution.

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  • Visibility of vortex core in fermionic superfluid with population imbalance

    M. Takahashi, T. Mizushima, K. Machida, M. Ichioka

    JOURNAL OF LOW TEMPERATURE PHYSICS   148 ( 3-4 )   423 - 427   2007.8

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    In Fermionic superfluids with a vortex, at T=0, the depletion of the atomic density appears in the core region, which is strongly associated with the discreteness of the core-bound state, called the Caroli-de Gennes-Matricon state. In imbalanced superfluid, however, it is found by the microscopic study based on the Bogoliubov-de Gennes approximation that this quantum depletion is progressively filled out in majority spin species as population imbalance increases. In contrast, the minority species keeps the depletion, which enables the direct observation of "superfluidity", because the quantized vortex is a hallmark of superfluidity.

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  • Vortex state in a Fulde-Ferrell-Larkin-Ovchinnikov superconductor based on quasiclassical theory

    Masanori Ichioka, Hiroto Adachi, Takeshi Mizushima, Kazushige Machida

    PHYSICAL REVIEW B   76 ( 1 )   014503 1-10   2007.7

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    We investigate the vortex state with Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) modulations suggested for a high-field phase of CeCoIn5. On the basis of quasiclassical Eilenberger theory, we calculate the three-dimensional structure of pair potentials, internal magnetic fields, paramagnetic moments, and electronic states for s-wave and d-wave pairings comparatively. The pi-phase shift of the pair potential at the FFLO nodal plane or at the vortex core induces sharp peak states in the local density of states and enhances the local paramagnetic moment. We also discuss the NMR spectrum and neutron scattering as methods to detect the FFLO structure.

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  • Quasi-classical calculation of the mixed-state thermal conductivity in s- and d-wave superconductors

    Hiroto Adachi, Predrag Miranovic, Masanori Ichioka, Kazushige Machida

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   76 ( 6 )   064708 1-7   2007.6

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    To see how superconducting gap structures affect the longitudinal component of mixed-state thermal conductivity K-xx(B), the magnetic-field dependences of K-xx(B) in s- and d-wave superconductors are investigated. Calculations are performed on the basis of the quasi-classical theory of superconductivity by fully taking account of the spatial variation of the normal Green's function, neglected in previous works, by the Brandt-Pesch-Tewordt approximation. On the basis of our result, we discuss the possibility of K-xx(B) measurement as a method of probing the gap structure.

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  • Vortex state in FFLO superconductors

    Masanori Ichioka, Hiroto Adachi, Takeshi Mizushima, Kazushige Machida

    JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS   310 ( 2 )   593 - 595   2007.3

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    Based on the quasiclassical theory, we investigate the vortex structure in the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state suggested for the high. field phase of CeCoIn5. We show that the paramagnetic moments are enhanced at the vortex line and at the nodal plane of the FFLO modulation, and discuss the double peak structure of the NMR spectrum in the FFLO state. (c) 2006 Elsevier B.V. All rights reserved.

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  • Quasiclassical calculation of the quasiparticle thermal conductivity in a mixed state

    Hiroto Adachi, Predrag Miranovic, Masanori Ichioka, Kazushige Machida

    JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS   310 ( 2 )   640 - 642   2007.3

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    We report the result of calculation of the quasiparticle thermal conductivity kappa(xx)(del T perpendicular to B) in the vortex state of a two-dimensional superconductor. We compute k(xx) for both s-wave and d-wave superconductors, taking account of the spatial dependence of normal Green's function g, which is neglected in the previous studies using the Brandt-Pesch-Tewordt (BPT) method. Our results indicate that k(xx) based on the BPT method is slightly underestimated due to its incoherent spatial averaging procedure. (c) 2006 Elsevier B.V. All rights reserved.

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  • Macroscopic manifestations of broken inversion symmetry in noncentrosymmetric superconductors with applied magnetic field

    Masatosi Oka, Masanori Ichioka, Kazushige Machida

    JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS   310 ( 2 )   575 - 577   2007.3

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    We numerically investigate paramagnetic properties in noncentrosymmetric superconductors under applied magnetic fields, based on the time-dependent Ginzburg-Landau theory including the Pauli paramagnetic effect and the Rashba interaction. When an applied field is perpendicular to the polar axis, the paramagnetic effect breaks centrosymmetry in the Meissner state and cylindrical symmetry in the vortices, as macroscopic manifestations of broken inversion symmetry in the spatial structures of the screening current and the penetrating field. The paramagnetic supercurrent exists even at the vortex center by their asymmetric properties, therefore the flux flow is spontaneously induced without applying external currents. (c) 2006 Published by Elsevier B.V.

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  • Theory of tunneling spectroscopy in the Larkin-Ovchinnikov state

    Yukio Tanaka, Yasuhiro Asano, Masanori Ichioka, Satoshi Kashiwaya

    PHYSICAL REVIEW LETTERS   98 ( 7 )   077001 1-4   2007.2

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    We present a theory of tunneling spectroscopy for normal metal/Larkin-Ovchinnikov state junctions in which the spatial periodic modulation in the pair potential amplitude is taken into account. The tunneling spectra show the characteristic line shapes reflecting the minigap structures under the periodic pair potentials depending on the boundary condition of the pair potentials at the junction interface. These features are qualitatively different from the tunneling spectra of the Fulde-Ferrell state. We propose an experimental setup which identifies the superconducting state of CeCoIn5.

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  • Thermal conductivity in the vortex state of s-wave and d-wave superconductors Reviewed

    Miranović P, Adachi H, Ichioka M, Machida K

    AIP Conference Proceedings   899   630 - 630   2007

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    Thermal conductivity in the vortex state has been calculated by solving self-consistently Eilenberger quasi-classical equations of superconductivity. Field dependence of thermal conductivity tensor has been calculated for various impurity parameters. We showed the difference in the field dependence between s-wave and d-wave superconductors.

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    Other Link: http://orcid.org/0000-0002-6844-6477

  • Effect of the vortices on the nuclear spin relaxation rate in the unconventional pairing states of the organic superconductor (TMTSF)(2)PF6

    M. Takigawa, M. Ichioka, K. Kuroki, Y. Asano, Y. Tanaka

    PHYSICAL REVIEW LETTERS   97 ( 18 )   2006.11

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    This Letter theoretically discusses quasiparticle states and nuclear spin relaxation rates T-1(-1) in the quasi-one-dimensional superconductor (TMTSF)(2)PF6 under a magnetic field applied parallel to the conduction chains. We study the effects of Josephson-type vortices on T-1(-1) by solving the Bogoliubov-de Gennes equation for p-, d- or f-wave pairing interactions. In the presence of line nodes in pairing functions, T-1(-1) is proportional to T in sufficiently low temperatures because quasiparticles induced by vortices at the Fermi energy relax spins. We also try to identify the pairing symmetry of (TMTSF)(2)PF6.

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  • Vortex-core structure in neutral fermion superfluids with population imbalance

    M. Takahashi, T. Mizushima, M. Ichioka, K. Machida

    PHYSICAL REVIEW LETTERS   97 ( 18 )   2006.11

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    Quantized vortex-core structure is theoretically investigated in fermion superfluids with population imbalance for two atom species of neutral atom clouds near a Feshbach resonance. In contrast with the vortex core in balance case where the quantum depletion makes a vortex visible through the density profile measurement, the vortex core is filled in and becomes less visible because the quantized discrete bound states are occupied exclusively by the majority species. Yet it is shown that the core can be visible through the minority density profile experiment using phase contrast imaging, revealing an interesting opportunity to examine low-lying fermionic core bound states unexplored so far.

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  • Electronic structure of vortex state in a FFLO superconductor

    Masanori Ichioka, Hiroto Adachi, Takeshi Mizushima, Kazushige Machida

    PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS   445   186 - 189   2006.10

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    Vortex states in a Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) superconductor are microscopically investigated by the quasi-classical Eilenberger theory. We calculate the spatial structure of the pair potential, paramagnetic magnetization (i.e., Knight shift in a magnetic field) and electronic states, including paramagnetic depairing effect in addition to the orbital depairing effect. Topologies of 2 pi phase winding at the vortex line and pi phase shift at the FFLO nodal plane affect the distribution of paramagnetic magnetization and low energy electronic states. We also discuss the NMR resonance line shape observed in the high field phase of CeCoIn5. (c) 2006 Elsevier B.V. All rights reserved.

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  • Electronic structures and NMR T-1(-1) in quasi-one-dimensional organic superconductor (TMTSF)(2)PF6

    M. Takigawa, M. Ichioka, K. Kuroki, Y. Tanaka, Y. Asano

    PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS   445   190 - 193   2006.10

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    On the basis of the Bogoliubov de Gennes theory, electronic structures around a vortex in quasi-one-dimensional organic superconductor (TMTSF)(2)PF6 are studied at the quarter-filling electron density in magnetic fields applied parallel to the conduction chain. We consider three pairing symmetries (d-, p- and f-wave) in superconductors. In d- and f-wave symmetries, nuclear relaxation rate T-1(-1) is proportional to temperatures because quasiparticles around the vortex relax spins. (c) 2006 Elsevier B.V. All rights reserved.

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  • Ubiquitous V-shape density of states in a mixed state of clean limit type II superconductors

    N. Nakai, P. Miranovic, M. Ichioka, H. F. Hess, K. Uchiyama, H. Nishimori, S. Kaneko, N. Nishida, K. Machida

    PHYSICAL REVIEW LETTERS   97 ( 14 )   2006.10

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    It is demonstrated theoretically and experimentally that the low energy density of states N(E) is described by a singular V-shape form N(E)=N-0(H)+alpha vertical bar E vertical bar+O(E-2) for all clean superconductors in a vortex state, irrespective of the underlying gap structure. The linear term alpha|E| which has not been recognized so far is obtained by exactly evaluating the vortex contribution. Based on microscopic Eilenberger theory N(E) is evaluated for the isotropic gap, line, and point-node gaps to yield a V-shape N(E). Scanning tunneling spectroscopy-STM experiments on NbSe2 and YNi2B2C give direct evidence for this. We provide arguments on the significance of this finding and on the relevance to other experiments.

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  • Generic phase diagram of Fermion superfluids with population imbalance

    K. Machida, T. Mizushima, M. Ichioka

    PHYSICAL REVIEW LETTERS   97 ( 12 )   2006.9

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    It is shown by microscopic calculations for trapped imbalanced Fermi superfluids that the gap function always has sign changes, i.e., the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO)-like state, up to a critical imbalance P(c), beyond which normal state becomes stable, at temperature T=0. A temperature-versus-pressure phase diagram is constructed, where the BCS state without sign change is stable only at T not equal 0. We reproduce the observed bimodality in the density profile to identify its origin and evaluate P(c) as functions of T and the coupling strength. These dependencies match with the recent experiments.

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  • Basal-plane magnetic anisotropies of high-k d-wave superconductors in a mixed state: A quasiclassical approach

    Hiroto Adachi, Predrag Miranovic, Masanori Ichioka, Kazushige Machida

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   75 ( 8 )   2006.8

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    We study the basal-plane anisotropies of reversible magnetization and torque in a mixed state of layered d-wave superconductors based on the quasiclassical version of the BCS-Gor'kov theory. Both the longitudinal magnetization (M-L) and torque (tau) show fourfold oscillations as a function of the field angle chi. The relationship between the node position and the oscillatory patterns shown by M-L and tau is clarified. It is also shown that the sign of the tau(chi)-oscillation does not change between H-c1 and H-c2, while the sign of the M-L(chi)-oscillation changes. The newly obtained result for tau indicates that the torque experiment can allow us to detect the in-plane anisotropies of H-c2 even in a material with strong fluctuations such as cuprate or organic superconductors, where the H-c2 itself cannot be determined experimentally.

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  • Surface and vortex structures in noncentrosymmetric superconductors under applied magnetic fields

    Masatosi Oka, Masanori Ichioka, Kazushige Machida

    PHYSICAL REVIEW B   73 ( 21 )   2006.6

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    We investigate how the macroscopic spatial structure of broken inversion symmetry manifests in noncentrosymmetric superconductors, by the microscopic broken inversion symmetry of the crystal structure. Based on the time-dependent Ginzburg-Landau theory including the Pauli paramagnetic effect and the Rashba interaction, we demonstrate that the centrosymmetric structures of the internal field and the screening current are broken macroscopically. The flow structure of paramagnetic supercurrent spontaneously induces the flux flow without applying external currents.

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  • Specific heat and low-lying excitations in the mixed state for a type-II superconductor

    N. Nakai, P. Miranovic, M. Ichioka, K. Machida

    PHYSICAL REVIEW B   73 ( 17 )   2006.5

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    Low temperature behavior of the electronic specific heat C(T) in the mixed state is by the self-consistent calculation of the Eilenberger theory. In addition to the gamma T-term (gamma is a Sommerfeld coefficient), C(T) has a significant contribution of T-2-term intrinsic in the vortex state. We identify the origin of the T-2 term as (i) V-shape density of states in the vortex state and (ii) the Kramer-Pesch effect of vortex-core shrinking upon lowering T. These results for both full-gap and line-node cases reveal that the vortex core is a richer electronic structure beyond the normal core picture.

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  • Fulde-Ferrell-Larkin-Ovchinnikov states in Fermi gases with unequal populations

    T. Mizushima, K. Machida, M. Ichioka

    LOW TEMPERATURE PHYSICS, PTS A AND B   850   79 - +   2006

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    We theoretically investigate the microscopic structure of neutral Fermionic systems with unequal atomic populations. By using fully microscopic Bogoliubov-de Gennes framework, we study on the vortex structure in a single-vortex state with and without the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) modulation of the pairing field. It is found that the novel local density of states structure appears at intersection point of the FFLO nodal plane and the vortex line, which reflects the topological structure of the pairing field.

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  • Electronic structure of vortex in the FFLO superconducting state

    Masanori Ichioka, Hiroto Adachi, Takeshi Mizushima, Kazushige Machida

    LOW TEMPERATURE PHYSICS, PTS A AND B   850   725 - 728   2006

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    Based on the quasiclassical theory, we investigate the vortex structure in the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state suggested to exist for the high field phase of CeCoIn5. The pair potential has 2 pi-phase winding around the vortex line, and x-phase shift at the nodal plane of the FFLO modulation. These topologies of the phase structure affect the distribution of paramagnetic moment and low energy electronic states. We also discuss the resonance line shape of the Knight shift in the FFLO state.

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  • 非対称粒子分布を持つフェルミ原子気体における FFLO 状態実現の可能性

    水島健, 市岡優典, 町田一成

    素粒子論研究   2006

  • Theory of gap-node detection by angle-resolved specific heat measurement

    P Miranovic, M Ichioka, K Machida, N Nakai

    JOURNAL OF PHYSICS-CONDENSED MATTER   17 ( 50 )   7971 - 7980   2005.12

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    The specific heat oscillation in the mixed state of type II superconductors is studied theoretically when rotating a field within a plane containing a gap minimum and maximum. The calculations are performed microscopically by solving the quasi-classical Eilenberger equation for vortex lattices. The field dependence of the oscillation amplitude can discriminate between the nodal and anisotropic gap with a finite minimum and the oscillation phase gives the gap minimum position on the Fermi surface. These also provide a way to separate out the anisotropic behaviour due to the Fermi velocity.

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  • Electronic structure and spontaneous internal field around nonmagnetic impurities in spin-triplet chiral p-wave superconductors

    M Takigawa, M Ichioka, K Kuroki, Y Tanaka

    PHYSICAL REVIEW B   72 ( 22 )   2005.12

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    The electronic structure around an impurity in spin-triplet p-wave superconductors is studied by the Bogoliubov-de Gennes theory on a tight-binding model, where we have chosen sin p(x)+i sin p(y)-wave or sin(p(x)+p(y))+i sin(-p(x)+p(y))-wave states, which are considered to be candidates for the pairing state in Sr2RuO4. We calculate the spontaneous current and the local density of states around the impurity and discuss the difference between the two types of pairing. We propose that it is possible to discriminate the two pairing states by studying the spatial dependence of the magnetic field around a pair of impurities.

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  • Spontaneous internal field around the non-magnetic impurity in spin-triplet p-wave superconductivity

    A Takigawa, M Ichioka, K Kuroki, Y Tanaka

    PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES   29 ( 3-4 )   619 - 623   2005.11

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    The electronic structure around an impurity in spin triplet p-wave superconductors is investigated by the Bogoliubov-de Gennes theory on a tight-binding model. We calculate the spontaneous current and the local density of states around the impurity and discuss the difference between sin p(x) + i sin p(y)-wave and sin(p(x) +p(y)) - i sin(-p(x) +p(y))-wave superconducting states. (c) 2005 Elsevier B.V. All rights reserved.

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  • Vortex core states in high-T-c superconductors with induced incommensurate spin and charge density waves

    M Ichioka, M Takigawa, K Machida

    PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS   426   28 - 35   2005.10

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    We investigate the change of the vortex structure in the presence of the induced stripe or checkerboard pattern modulation of the incommensurate spin density wave (SDW) and charge density wave (CDW) around the vortex core. The order parameter and the quasiparticle structure in the vortex lattice state are calculated by Bogoliubov-de Gennes theory on a two-dimensional Hubbard model with nearest-neighbor site pairing interaction. By the induced SDW and CDW, low-energy excitations around the vortex core are suppressed, producing "empty core" structure, as observed by the scanning tunneling microscopy. In the relation to these quasiparticle structures, we discuss the site-selective nuclear spin relaxation time T, and thermal conductivity in the vortex state. (c) 2005 Elsevier B.V. All rights reserved.

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  • Topological structure of a vortex in the Fulde-Ferrell-Larkin-Ovchinnikov state

    T Mizushima, K Machida, M Ichioka

    PHYSICAL REVIEW LETTERS   95 ( 11 )   2005.9

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    We find theoretically that the vortex core in the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state is quite different from the ordinary core for a simple topological reason. The intersection point of a vortex and nodal plane of the FFLO state empties the excess spins. This leads to observable consequences in the spatial structure of the spontaneous magnetization. We analyze this topological structure based on the low lying excitation spectrum by solving a microscopic Bogoliubov-de Gennes equation to clarify its physical origin.

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  • Theoretical study on the field dependence of the zero energy density of states in an anisotropic gap superconductors

    N Nakai, P Miranovic, M Ichioka, K Machida

    JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS   66 ( 8-9 )   1362 - 1364   2005.8

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    Based on the quasi-classical theory, we calculate the zero energy density of states N(B) in the mixed state for a type 11 superconductor. N(B) is related to the sommerfeld coefficient gamma(B), which gives us useful information for a superconducting gap. The linear portion in gamma(B) relative to B,2 and its slope in a low field reflect the gap anisotropy, so that we can distinguish the nodal gap and the anisotropic full gap, and estimate the magnitude of the gap anisotropy. (c) 2005 Published by Elsevier Ltd.

    DOI: 10.1016/j.jpcs.2005.05.011

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  • Mixed-state thermodynamics of superconductors with moderately large paramagnetic effects

    H Adachi, M Ichioka, K Machida

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   74 ( 8 )   2181 - 2184   2005.8

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    Effects of Pauli paramagnetism on thermodynamic quantities in a vortex state, such as the specific heat C and magnetization M, are studied using the quasiclassical Eilenberger formalism. We demonstrate that with an increase of paramagnetic depairing effect, the sigh of the curvature of the field dependence of C changes from negative to positive, and that the Maki parameter kappa(2) becomes an increasing function of temperature. Our results provide a natural explanation for the unusual field dependence of C seen in CeCoIn5 in terms of the paramagnetic effect.

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  • Fulde-Ferrell-Larkin-Ovchinnikov states in a superfluid Fermi gas

    T Mizushima, M Ichioka, K Machida

    JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS   66 ( 8-9 )   1359 - 1361   2005.8

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    Recently, both the experimental and theoretical studies to realize superfluid states in atomic gases have been performed by using a 50-50 mixture of atoms in two hyperfine spin states. We discuss favorable superfluid states in an unequal mixture. Such situation is analogous to a superconducting state in the presence of a magnetic field acting on the electron spins and then the natural candidate for the ground state is known as the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state which is a spatially inhomogeneous superfluid state. We examine the possibility of the FFLO state in two species gas of Fermions confined in a realistic three-dimensional harmonic trap. We propose a clear experimental way to create and directly detect the spatially modulated FFLO state from the macroscopic signature. (c) 2005 Elsevier Ltd. All rights reserved.

    DOI: 10.1016/j.jpcs.2005.05.067

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  • Magnetization process in a chiral p-wave superconductor with multidomains

    M Ichioka, Y Matsunaga, K Machida

    PHYSICAL REVIEW B   71 ( 17 )   2005.5

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    A simulation study for the magnetization process is performed for the multidomain state in a chiral p-wave superconductor, using the time-dependent Ginzburg-Landau theory. The external field penetrates inside as cureless vortices through the domain wall, forming the vortex sheet structure. We find that, with increasing magnetic fields, the domain walls move so that the unstable domains shrink to vanish. Therefore, the single domain structure is realized at higher fields.

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  • Double transition and vortex-sheet structure in multi-component superconductors

    M Ichioka, Y Matsunaga, K Machida

    PHYSICA B-CONDENSED MATTER   359   539 - 541   2005.4

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    A simulation study using the time-dependent Ginzburg Landau theory is performed for the vortex state in two-component superconductors, in order to investigate the nature of the double transition and exotic vortex state, such as the vortex structure at the domain wall. Half flux-quantum vortices are aligned along the domain wall, forming vortex-sheet structure. The flux flow and the pinning of the vortex sheet are also investigated. (c) 2005 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.physb.2005.01.140

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  • Anisotropic diamagnetic response in type-II superconductors with gap and Fermi-surface anisotropies

    H Adachi, P Miranovic, M Ichioka, K Machida

    PHYSICAL REVIEW LETTERS   94 ( 6 )   2005.2

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    The effects of anisotropic gap structures on a diamagnetic response are investigated in order to demonstrate that the field-angle-resolved magnetization [M-L (chi)] measurement can be used as a spectroscopic method to detect gap structures. Our microscopic calculation based on the quasiclassical Eilenberger formalism reveals that M-L (chi) in a superconductor with a fourfold gap displays a fourfold oscillation reflecting the gap and Fermi-surface anisotropies, and the sign of this oscillation changes at a field between H-c1 and H-c2. As a prototype of unconventional superconductors, magnetization data for borocarbides are also discussed.

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  • Direct imaging of spatially modulated superfluid phases in atomic fermion systems

    T Mizushima, K Machida, M Ichioka

    PHYSICAL REVIEW LETTERS   94 ( 6 )   2005.2

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    It is proposed that the spatially modulated superfluid phase, or the Fulde-Ferrell-Larkin-Ovchinnikov state could be observed in resonant fermion atomic condensates which are realized recently. We examine optimal experimental setups to achieve it by solving the Bogoliubov-de Gennes equation for both idealized one-dimensional and realistic three-dimensional cases. The spontaneous modulation of this superfluid is shown to be directly imaged as the density profiles either by optical absorption or by Stern-Gerlach experiments.

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  • Collective oscillations of vortices in Bose-Einstein condensates under rotation

    K Machida, T Mizushima, M Ichioka

    LASER PHYSICS   15 ( 4 )   660 - 668   2005

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    We investigate low-energy collective excitations in Bose-Einstein condensates (BECs) with a single-vortex line or many vortices by using the microscopic theory based on the Bogoliubov-Popov formalism. The paper is divided into the following two section: (i) We first study the damping process of the quadrupole modes in a three-dimensional cigar-shaped BEC. The selective excitation of such the modes occurs during the rotation of the condensate in the opposite or same direction relative to a vortex velocity field. The dramatic change of the damping process of these modes is explained by the linear response theory. It is proposed that Kelvin modes play a leading part in the decay process of the quadrupole excitation. These results are quantitatively compared with the recent experiment on Rb-87 by Bretin et aL [Phys. Rev. Lett. 90, 100403 (2003)]. (ii) In addition, the complete spectrum of the collective excitations in vortex-lattice states is obtained by solving the Bogoliubov-de Gennes equation in a two-dimensional disk-shaped BEC. We also discuss the frequency shift of totally symmetric and twofold symmetric Tkachenko modes.

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  • Electronic state around vortex in a two-band superconductor Reviewed

    Masanori Ichioka, Kazushige Machida, Noriyuki Nakai, Predrag Miranović

    Physical Review B - Condensed Matter and Materials Physics   70 ( 14 )   1 - 144508   2004.10

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    Based on the quasiclassical theory, we investigate the vortex state in a two-band superconductor with a small gap on a three-dimensional Fermi surface and a large gap on a quasi-two dimensional one, as in MgB2. The field dependence of zero-energy density of states is compared for fields parallel and perpendicular to the ab plane, and the anisotropy of the vortex core shape is discussed for a parallel field. The Fermi surface geometry of two bands, combining the effect of the normal-like electronic state on the small gap band at high fields, produces characteristic behavior in the anisotropy of c and ab directions.

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  • Flux flow and pinning of the vortex sheet structure in a two-component superconductor Reviewed

    Yasushi Matsunaga, Masanori Ichioka, Kazushige Machida

    Physical Review B - Condensed Matter and Materials Physics   70 ( 10 )   1 - 100502   2004.9

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    A simulation study using the time-dependent Ginzburg-Landau theory is performed for the vortex state in two-component superconductors, such as PrOs4Sb12. We investigate the flux flow and the pinning of the vortex sheet structure. We find a domain wall that traps half flux-quantum vortices and moves with the flux flow. In the pinning case, we observe an emitting process of a conventional vortex from the vortex sheet by combining a pair of half flux-quantum vortices.

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  • Field dependence of the zero-energy density of states around vortices in an anisotropic-gap superconductor Reviewed

    N. Nakai, P. Miranović, M. Ichioka, K. Machida

    Physical Review B - Condensed Matter and Materials Physics   70 ( 10 )   1 - 100503   2004.9

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    It is shown theoretically that the Sommerfeld coefficient γ(B) in the mixed state contains useful information on the gap topology in a superconductor. We accurately evaluate γ(B) against magnetic induction B by using microscopic quasiclassical theory. The linear portion in γ(B) relative to 5c2 and its slope in low field faithfully corresponds to the gap anisotropy, so that we can distinguish the nodal gap and the anisotropic full gap, and estimate the magnitude of the gap anisotropy.

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  • Effects of nonmagnetic scatterers on the local density of states around a vortex in s-wave superconductors Reviewed

    P. Miranović, M. Ichioka, K. Machida

    Physical Review B - Condensed Matter and Materials Physics   70 ( 10 )   1 - 104510   2004.9

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    We study the effect of nonmagnetic impurities on the local density of states (LDOS) in the mixed state of s-wave superconductors. The quasiclassical equations of superconductivity in the vortex state are solved self-consistently to show how the LDOS evolves with impurity concentration. The spatially averaged zero-energy LDOS is a linear function of magnetic induction in low fields, N(E=0)=α(τ)B/Hc2, for all impurity concentrations. The coefficient α depends weakly on the electron mean-free path. We evaluate numerically the differential conductance and spatial profiles of zero-energy LDOS, which can help in extracting the mean-free path from the measured LDOS.

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  • Quasiparticle heat transport in mixed state of high-T-c superconductors

    M Takigawa, M Ichioka, K Machida

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   73 ( 8 )   2049 - 2052   2004.8

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    The field dependence of low-temperature thermal conductivity kappa(H) observed on cuprates is explained by calculating kappa(H) microscopically. The heat current carried by low-lying quasiparticles around a vortex core decreases with H due to its depletion by the H-induced moment centered at a core for an underdoped case. This leads to a common and consistent picture on an "anomalous core". kappa(H, T) is found to be a useful tool for probing quasiparticle structures in the mixed state in general.

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  • Thermal conductivity of the vortex lattice state involving the antiferromagnetism around the core Reviewed

    M Takigawa, M Ichioka, K Machida

    PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS   404 ( 1-4 )   375 - 379   2004.5

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    The thermal conductivity kappa(chichi) is the difference between higher and lower temperature regions, because the spatially-resolved thermal conductivity kappa(chichi)(r) is localized around the vortex core at lower temperature and delocalized at higher temperature. On one hand, much attention is focused on the spin and charge ordering around the vortex. When the antiferromagnetism appears around the core, the energy gap suppresses the density of states on the Fermi energy, and the zero-energy peak at the vortex core splits or vanishes. The kappa(chichi) under the Neel temperature is suppressed by the antiferromagnetism. We solve the Bogoliubov-de Gennes equation self-consistently by two-dimensional extended Hubbard model including the repulsive interaction U, and calculate the on the basis of the linear response theory. The picture of the spatial variation of the thermal conductivity kappa(r) through the spin resolved local DOS well explains recent experiments. (C) 2004 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.physc.2003.09.091

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  • Vortex state in double transition superconductors

    Y Matsunaga, M Ichioka, K Machida

    PHYSICAL REVIEW LETTERS   92 ( 15 )   2004.4

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    The novel vortex phase and nature of the double transition field are investigated by two-component Ginzburg-Landau theory in a situation where fourfold-twofold symmetric superconducting double transition occurs. The deformation from 60degrees triangular vortex lattice and a possibility of the vortex sheet structure are discussed. In the presence of the gradient coupling, the transition changes to a crossover at finite field. These characters are important to identify the multiple superconducting phase in PrOs4Sb12.

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  • Expansion of vortex cores by strong electronic correlation in La2-xSrxCuO4 at low magnetic induction

    R Kadono, W Higemoto, A Koda, MI Larkin, GM Luke, AT Savici, YJ Uemura, KM Kojima, T Okamoto, T Kakeshita, S Uchida, T Ito, K Oka, M Takigawa, M Ichioka, K Machida

    PHYSICAL REVIEW B   69 ( 10 )   2004.3

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    The vortex core radius rho(v), defined as the peak position of the supercurrent around the vortex, has been determined by muon spin rotation measurements in the mixed state of La2-xSrxCuO4 for x=0.13, 0.15, and 0.19. At lower doping (x=0.13 and 0.15), rho(v)(T) increases with decreasing temperature T, which is opposite to the behavior predicted by the conventional theory. Moreover, rho(v)(T--&gt;0) is significantly larger than the Ginzburg-Landau coherence length determined by the upper critical field, and shows a clear tendency to decrease with increasing the doping x. These features can be qualitatively reproduced in a microscopic model involving antiferromagnetic electronic correlations.

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  • Quasiparticle structure in antiferromagnetism around the vortex and nuclear magnetic relaxation time

    M Takigawa, M Ichioka, K Machida

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   73 ( 2 )   450 - 458   2004.2

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    On the basis of the Bogoliubov-de Gennes theory for the two-dimensional extended Hubbard model, the vortex structure in d-wave superconductors is investigated including the contribution of the induced incommensurate antiferromagnetism around the vortex core. As the on-site repulsive interaction U increases, the spatial structure of charge and spin changes from the antiferromagnetic state with checkerboard modulation to that with the stripe modulation. By the effect of the induced antiferromagnetic moment, the zero-energy density of states is suppressed, and the vortex core radius increases. We also study the effect of the local density of states (LDOS) change on the site-dependent nuclear relaxation rate T-1(-1)(r). These results are compared with a variety of experiments performed on high T-c cuprates.

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  • Beliaev damping of transverse quadrupole oscillations in single-vortex Bose-Einstein condensates

    T Mizushima, M Ichioka, K Machida, T Isoshima, MM Salomaa

    LASER PHYSICS   14 ( 2 )   295 - 301   2004.2

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    We investigate the damping mechanism of two transverse quadrupole oscillations in the single-vortex state of Bose-Einstein condensates using the linear response theory. It is demonstrated theoretically that the Kelvin modes as a propagation wave along a vortex line can be excited via Beliaev damping processes for only the counter-rotating quadrupole mode. We calculate the spectral weight of the density-response function within the Boooliubov-Popov theory in a cylindrical system taking into account both Beliaev and Landau processes. Furthermore, we extend these considerations to the full 3D cigar-shaped system, which enables us to discuss the effects of the longitudinal confinement on the damping processes. These results are compared with the recent experiment on Rb-87 by Bretin et al.

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  • Fermi arc of metallic diagonal stripes in high-temperature superconducting cuprates

    E Kaneshita, M Ichioka, K Machida

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   72 ( 10 )   2441 - 2444   2003.10

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    Spectral weight is investigated for the metallic diagonal stripe state in a two-dimensional Hubbard model, and the Fermi arc observed by the angle-resolved photoemission spectroscopy of La2-xSrxCuO4 is discussed. The Fermi arc coming from the midgap state of a diagonal stripe appears near (pi/2, pi/2) and at the equivalent positions in the reciprocal space, and the gap opens below the midgap state. We show how this spectral weight structure depends on the phasing of stripes, i.e., site- or bond-centered stripes.

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  • Excitation spectra of Bose-Einstein condensates in optical lattice

    M Ichioka, K Machida

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   72 ( 9 )   2137 - 2140   2003.9

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    The excitation spectra of Bose-Einstein condensates arc investigated in a three-dimensional optical lattice by the Bogoliubov theory considering the original sinusoidal potential for the optical lattice. When the lattice potential becomes high, the excitations show softening at large wavelengths, suggesting the breakdown of superfluidity. We also study the filling and interaction dependences of the properties of the excitation spectra and one-dimensional lattice case.

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  • Orientational field dependence of low-lying excitations in the mixed state of unconventional superconductors

    P Miranovic, N Nakai, M Ichioka, K Machida

    PHYSICAL REVIEW B   68 ( 5 )   2003.8

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    Orientational field dependence of the zero-energy density of states (ZEDOS) is calculated for superconductors with the polar state (line node), axial state (point node), and three-dimensional d-wave state. Depending on the gap topology and the relative field direction the field dependencies of ZEDOS sensitively differ, providing us a useful and practical method to identify the gap topology. It is also demonstrated that for d-wave state the field rotation in the basal plane shows a sizable oscillation (similar to3%) of ZEDOS. This is directly measurable in low-T specific heat experiment in the mixed state.

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  • Dispersive gap mode of phonons in anisotropic superconductors

    M Ichioka, K Machida

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   72 ( 8 )   2064 - 2070   2003.8

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    We estimate the effect of the superconducting gap anisotropy in the dispersive gap mode of phonons, which is observed by the neutron scattering on borocarbide superconductors. We numerically analyze the phonon spectrum considering the electron-phonon coupling, and examine contributions coming from the gap suppression and the sign change of the pairing function on the Fermi surface. When the sign of the pairing function is changed by the nesting translation, the gap mode does not appear. We also discuss the suppression of the phonon softening of the Kohn anomaly due to the onset of superconductivity. We demonstrate that observation of the gap dispersive mode is useful for sorting out the underlying superconducting pairing function.

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  • On superconducting double transition in PrOs4Sb12

    M Ichioka, N Nakai, K Machida

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   72 ( 6 )   1322 - 1325   2003.6

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    Superconducting double transition in PrOs4Sb12 is investigated by analyzing the anisotropy of the upper critical field H-c2 in the ab-plane, and the possible pairing state is discussed. When mixing due to gradient coupling is active, the twofold-symmetric component is necessarily induced in the fourfold symmetric phase, leading to the twofold oscillation of H-c2, contrary to the experimental result. To avoid the mixing effect, the weak spin-orbit coupling triplet pairing state is considered as a likely pairing function, where time-reversal symmetry is broken.

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  • Microscopic study of low-kappa type-II superconductors

    P Miranovic, N Nakai, M Ichioka, K Machida

    PHYSICA B-CONDENSED MATTER   329   1382 - 1383   2003.5

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    Thermodynamics and vortex lattices of low-kappa type-II superconductors are studied numerically within the Eilenberger equations of superconductivity. Below some critical value kappa(c)(T) of the Ginzburg-Landau parameter kappa = lambda/xi, there is a first-order transition at H-c1 (type-IIa superconductivity) as a consequence of attractive vortex-vortex interaction. For kappa &gt; kappa(c) the phase transition is of the second order (type-IIb superconductivity). The phase boundary kappa(c)(T) that separates type-IIa and IIb superconductivity is calculated. (C) 2003 Elsevier Science B.V. All rights reserved.

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  • Beliaev damping and Kelvin mode spectroscopy of a Bose-Einstein condensate in the presence of a vortex line

    T Mizushima, M Ichioka, K Machida

    PHYSICAL REVIEW LETTERS   90 ( 18 )   2003.5

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    It is demonstrated theoretically that the counter-rotating quadrupole mode in a vortex of Bose-Einstein condensates can decay into a pair of Kelvin modes via the Beliaev process. We calculate the spectral weight of a density-response function within the Bogoliubov framework, taking account of both Beliaev and Landau processes. Good agreement with experiment on Rb-87 by Bretin et al. [Phys. Rev. Lett. 90, 100403 (2003)] allows us to unambigiously identify the decayed mode as the Kelvin wave propagating along a vortex line.

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  • Theoretical study on vortex lattices in tetragonal superconductors

    N Nakai, P Miranovic, M Ichioka, K Machida

    PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS   388   677 - 678   2003.5

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    Vortex lattices of four fold symmetric superconductors are studied numerically on the basis of the quasiclassical theory. The four fold symmetric anisotropy of the Fermi velocity or the superconducting gap function causes the vortex lattice transformation. The transformation as observed in LuNi2B2C could be understood with the four fold symmetric anisotropy. We show the temperature and field phase diagram for four fold symmetric superconductors and the spatial structures of the pair potential and zero energy states in the case of the stable square vortex lattice at the low field. (C) 2003 Elsevier Science B.V. All rights reserved.

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  • Field dependence of vortex structure in p(x) +/- ip(y)-wave superconductors

    M Ichioka, K Shiroyama, K Machida

    PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS   388   517 - 518   2003.5

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    To understand the vortex states in Sr2RuO4, we investigate differences of the vortex structure for two chiral pairings p(x) +/- ip(y), using quasi-classical Eilenberger theory and the Ginzburg-Landau theory. The induced opposite chiral component of the pair potential plays an important role in the vortex structure. It produces an rootH-behavior of the zero-energy density of states at higher field. We also consider the anisotropic case of the Fermi surface and superconducting gap. (C) 2003 Elsevier Science B.V. All rights reserved.

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  • Multiple components of the order parameter induced around the d(x2)-(y2)-wave vortex core

    M Takigawa, M Ichioka, K Machida

    PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS   388   667 - 668   2003.5

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    On the basis of the Bogoliubov-de Gennes theory for the two-dimensional extended Hubbard model, the vortex structure of d(x2-y2)-wave superconductors is analyzed. Multiple components of the order parameter are induced around the d(x2-y2)-wave vortex core. We study the spatial structure of the induced p(x) +/- ip(y) and extended s-wave components. We also study the case when the antiferromagnetism (checkerboard or stripe) is induced at the vortex core. There, spin-triplet d(x2-y2)-wave component is also induced. (C) 2003 Elsevier Science B.V. All rights reserved.

    DOI: 10.1016/S0921-4534(02)02438-3

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  • Study of phonon anomalies in stripe phase of high T-c cuprates

    E Kaneshita, M Ichioka, K Machida

    PHYSICA B-CONDENSED MATTER   329   777 - 778   2003.5

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    We theoretically investigate phonon anomalies in various high T-c cuprates in terms of stripe concept. They could be caused by coupling with charge translational modes of stripes. The phonon self-energy correction is evaluated by taking into account the collective stripe modes. The coupling with stripes causes a phonon dispersion gap when the phonon dispersion has a steep slope around 2Q. No gap appears when the phonon spectrum has a flat dispersion around 2Q. Thus it turns out that these are depending on the slope of the phonon dispersions. (C) 2003 Published by Elsevier Science B.V.

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  • Theoretical studies on vortices in unconventional and conventional superconductors

    K Machida, M Ichioka, P Miranovic, M Takigawa, N Nakai

    ACTA PHYSICA POLONICA B   34 ( 2 )   545 - 548   2003.2

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    Vortex imaging method by the site selective NMR is explained by self-consistently solving the Bogoliubov-de Gennes equation for both s-wave and d-wave pairings. We analyze the temperature dependence of the relation time T-1 using the resonance frequency at the intensity maximum, namely the saddle point T-1 experiments. The site selective T-1 data are shown to yield valuable information on low-lying electronic excitations around a vortex core.

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  • NMR relaxation time around a vortex in stripe superconductors

    M Takigawa, M Ichioka, K Machida

    PHYSICAL REVIEW LETTERS   90 ( 4 )   2003.1

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    Site-dependent NMR relaxation time T-1(r) is calculated in the vortex state using the Bogoliubov-de Gennes theory, taking account of possible "field-induced stripe" states in which the magnetism arises locally around a vortex core in d-wave superconductivity. The recently observed huge enhancement T-1(-1)(r) below T-c at a core site in Tl2Ba2CuO6 is explained. The field-induced stripe picture explains consistently other relevant STM and neutron experiments.

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  • Reentrant vortex lattice transformation in fourfold symmetric superconductors

    N Nakai, P Miranovic, M Ichioka, K Machida

    PHYSICAL REVIEW LETTERS   89 ( 23 )   2002.12

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    The physics behind the rhombic--&gt;square--&gt;rhombic flux line lattice transformation in increasing fields is clarified on the basis of Eilenberger theory. We demonstrate that this reentrance observed in LuNi2B2C is due to intrinsic competition between the superconducting gap and Fermi surface anisotropies. The calculations not only reproduce it but also predict the not yet found lock-in transition to a square lattice with different orientation in a higher field. In view of the physical origin given, this sequence of transitions is rather generic to occur in fourfold symmetric superconductors.

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  • Vortex lattice structures in superconductors with four-fold symmetric anisotropies

    Nakai N, Miranovic P, Ichioka M, Machida K

    Meeting abstracts of the Physical Society of Japan   57 ( 2 )   477 - 477   2002.8

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  • Magnetization process in chiral p-wave superconductors

    Ichioka M., Machida K.

    Meeting abstracts of the Physical Society of Japan   57 ( 2 )   419 - 419   2002.8

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  • Loc533al density of states in superconducting stripe states

    Ichioka M, Machida K

    Meeting abstracts of the Physical Society of Japan   57 ( 2 )   533 - 533   2002.8

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  • Quasiparticle Excitations and NMR around a Antiferro-magnetic Vortex Core

    Takigawa Mitsuaki, Ichioka Masanori, Machida Kazushige

    Meeting abstracts of the Physical Society of Japan   57 ( 2 )   477 - 477   2002.8

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  • Superconducting gap modulation in weak stripe states

    M Ichioka, K Machida

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   71 ( 8 )   1836 - 1839   2002.8

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    The superconducting gap modulation is investigated in the presence of a weak stripe structure, using the Boooliubov-de Gennes theory on the two-dimensional Hubbard model with nearest-neighbor site pairing interaction. We calculate the local density of states and discuss the recently observed scanning tunneling spectroscopy data suggesting four-lattice periodicity on Bi2Sr2CaCu2O8+delta. We also consider the spectral weight in the reciprocal space, where the Fermi surface and the Superconducting gap are modulated by the band-folding effect of the stripe structure.

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  • Vortex structure in Sr2RuO4

    M Takigawa, M Ichioka, K Machida, M Sigrist

    JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS   63 ( 6-8 )   1333 - 1336   2002.6

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    The vortex structure in p-wave superconductors is investigated by the Bogoliubov-de Gennes theory on a tight-binding model. We calculate the temperature dependence of the electronic state at each site in the vortex lattice state, and show the difference between sin p(x) + i sin p(y)-wave and sin p(x) - i sin p(y)-wave superconducting state. Furthermore the relation of the electronic structure and the site-dependence of the nuclear magnetic relaxation time is also discussed. (C) 2002 Elsevier Science Ltd. All rights reserved.

    DOI: 10.1016/S0022-3697(02)00086-0

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  • Dynamical properties of stripes

    E Kaneshita, R Morino, M Ichioka, K Machida

    JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS   63 ( 6-8 )   1545 - 1548   2002.6

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    The dynamical properties of stripes in high T-c oxide superconductors are studied theoretically at finite temperature (T) within RPA scheme on the two-dimensional Hubbard model. It is found that at lower dopings, the transverse dynamical susceptibility in the antiferromagnetic state exhibits the anomalous broadening of the spin wave spectral line width upon lowering T, indicating a phase transition to an incommensurate state. At a higher doping, the detailed T-evolutions of the spin wave spectrum are studied. (C) 2002 Elsevier Science Ltd. All rights reserved.

    DOI: 10.1016/S0022-3697(02)00074-4

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  • Field dependence of the vortex structure in chiral p-wave superconductors Reviewed

    M Ichioka, K Machida

    PHYSICAL REVIEW B   65 ( 22 )   2002.6

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    To investigate the different vortex structures between two chiral pairings p(x)+/-ip(y), we calculate the pair potential, the internal field, the local density of states, and the free energy in a vortex lattice state based on the quasiclassical Eilenberger theory, and analyze the magnetic-field dependence. The induced opposite chiral component of the pair potential plays an important role in the vortex structure. It also produces an rootH behavior of the zero-energy density of states at higher field. These results are helpful when we understand the vortex states in Sr2RuO4.

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  • 24aWB-5 Quasiparticle Excitations and NMR around a Antiferro-magnetic Vortex Core

    Takigawa Mitsuaki, Ichioka Masanori, Machida Kazushige

    Meeting abstracts of the Physical Society of Japan   57 ( 1 )   463 - 463   2002.3

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  • 24aWB-1 Field dependence of the vortex stricture in p-wave superconductors 2

    Ichioka M., Shiroyama K., Machida K.

    Meeting abstracts of the Physical Society of Japan   57 ( 1 )   462 - 462   2002.3

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  • 24aWB-3 Anisotropy of a superconducting gap and vortex lattice structure

    Nakai N., Miranovic P., Ichioka M., Machida K.

    Meeting abstracts of the Physical Society of Japan   57 ( 1 )   462 - 462   2002.3

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  • 24aWB-2 Stability of square vortex lattice in cubic and tetragonal superconductors

    Meeting abstracts of the Physical Society of Japan   57 ( 1 )   462 - 462   2002.3

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  • Phonon anomalies due to collective stripe modes in high T-c cuprates

    E Kaneshita, M Ichioka, K Machida

    PHYSICAL REVIEW LETTERS   88 ( 11 )   2002.3

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    Phonon anomalies observed in various high T-c cuprates by neutron experiments are analyzed theoretically in terms of the stripe concept. The phonon self-energy correction is evaluated by taking into account the charge collective modes of stripes, giving rise to dispersion gap, or kink and shadow phonon modes at twice the wave number of spin stripe. These features coincide precisely with observations. The gapped branches of the phonon are found to be in-phase and out-of-phase oscillations relative to the charge collective mode.

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  • Vortex structure in P-wave superconductors based on tight-binding model

    N Nakai, M Takigawa, M Ichioka, K Machida

    PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS   367 ( 1-4 )   50 - 53   2002.2

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    The spatial structure of the pair potential and the electronic state around a vortex is self-consistently calculated by the Bogoliubov-de Gennes theory on a tight-binding model with spin-triplet pairing interaction. We discuss the differences of the vortex structure for two chiral superconductivity of p(x) +/- ip(y)-wave, and the effects of the interband Cooper pair transfer on the vortex structure. (C) 2002 Elsevier Science B.V. All rights reserved.

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  • Thermal conductivity in the vortex lattice of d-wave and s-wave superconductors

    M Takigawa, M Ichioka, K Machida

    PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS   367 ( 1-4 )   46 - 49   2002.2

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    Thermal conductivity kappa(xx)(T) under a field is calculated by using a microscopic theory based on Bogoliubov-de Gennes equation for describing vortices and linear response theory. Superconductors with d(x2-y2)-wave and s-wave pairings are comparatively studied, modeled by a tight-binding extended Hubbard Hamiltonian in two spatial dimensions. The whole T-dependence of kappa(xx)(T) is calculated and shows the characteristic T-linear behavior in the lower T. This behavior is analyzed by examining the spatially resolved thermal flow patterns around a vortex. (C) 2002 Elsevier Science B.V. All rights reserved.

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  • Vortex structure in chiral p-wave superconductors Reviewed

    Masanori Ichioka, Kazushige Machida

    Physical Review B - Condensed Matter and Materials Physics   65 ( 1 )   145081 - 145089   2002.1

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    We investigate the vortex structure in chiral p-wave superconductors by the Bogoliubov-de Gennes theory on a tight-binding model. We calculate the spatial structure of the pair potential and electronic state around a vortex, including the anisotropy of the Fermi surface and superconducting gap structure. The differences of the vortex structure between sin px+i sin py-wave and sin px-i sin py-wave superconductors are clarified in the vortex lattice state. We also discuss the winding ∓3 case of the sin(px+py)±i sin(-px+py)-wave superconductivity.

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  • Soliton excitations in halogen-bridged mixed-valence binuclear metal complexes

    S Yamamoto, M Ichioka

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   71 ( 1 )   189 - 196   2002.1

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    Motivated by recent stimulative observations in halogen (X)-bridged binuclear transition-metal (M) complexes, which are referred to as MMX chains, we study solitons in a one-dimensional three-quarter-filled charge-density-wave system with both intrasite and intersite electron-lattice couplings. Two distinct ground states of MMX chains are reproduced and the soliton excitations on them are compared. In the weak-coupling region, all the solitons are degenerate to each other and are uniquely scaled by the band gap, whereas in the strong-coupling region, they behave differently deviating from the scenario in the continuum limit. The soliton masses are calculated and compared with those for conventional mononuclear MX chains.

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  • Field dependence of electronic specific heat in two-band superconductors

    N Nakai, M Ichioka, K Machida

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   71 ( 1 )   23 - 26   2002.1

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    The vortex structure is studied in light of MgB2 theoretically based on a two-band superconducting model by means of Bogoliubov-de Gennes framework. The field dependence of the electronic specific heat coefficient gamma(H) is focused. The exponent alpha in gamma(H) alphaH(alpha) is shown to become smaller by adjusting the gap ratio of the two gaps on the major and minor bands. The observed extremely small value alpha similar to 0.23 could be reasonable in this two-band model with the gap ratio similar to0.3.

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  • Vortex structure in chiral p-wave superconductors

    M Takigawa, M Ichioka, K Machida, M Sigrist

    PHYSICAL REVIEW B   65 ( 1 )   2002.1

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    We investigate the vortex structure in chiral p-wave superconductors by the Bogoliubov-de-Gennes theory on a tight-binding model. We calculate the spatial structure of the pair potential and electronic state around a vortex, including the anisotropy of the Fermi surface and superconducting gap structure, The differences of the vortex structure between sin p(x)+i sin p(y)-wave and sin p(x)-i sin p(y)-wave superconductors are clarified in the vortex lattice state. We also discuss the winding -/+3 case of the sin(p(x)+p(y))=i sin(-p(x)+p(y))-wave superconductivity.

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  • Magnetic field dependence of the vortex structure based on the microscopic theory Reviewed

    M Ichioka, M Takigawa, K Machida

    VORTICES IN UNCONVENTIONAL SUPERCONDUCTORS AND SUPERFLUIDS   132   225 - 242   2002

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    We investigate the vortex structure in the vortex lattice state by the self-consistent numerical calculation based on the microscopic theory, and focus on the magnetic field dependence. First, we study the vortex structure Comparatively for the s-wave and the d(x2)-(y2)-wave pairing cases by the quasi-classical Eilenberger theory. We show the spatial variation of the local density of states (LDOS), and discuss the field dependence of the spatially averaged density of states, vortex core radius, and internal field distribution. Second, we propose the site-selective NMR relaxation time measurement as a new method to observe the quasiparticle state around the vortex core. We explain the relation between the LDOS and the temperature dependence, of the site-selective T-1 based on the Bogoliubov-de Gennes theory, and discuss the field dependence of the T-1-behavior.

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  • Unconventional superconductivity with either multi-component or multi-band, or with chirality Reviewed

    K Machida, M Ichioka, M Takigawa, N Nakai

    RUTHENATE AND RUTHENO-CUPRATE MATERIALS   603   32 - 45   2002

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    In this review article, we discuss unconventional superconductivity where the unconventionality comes either from the multi-component order parameter, or from the multi-band order parameter, or from the chirality of the pairing function. These three typical form of unconventional superconductivity are analyzed in connection with materials such as UPt3 and UGe2 as the first example. MgB2 is mentioned as the second case where two distinctive energy gaps exist on different Fermi surface sheets. Sr2RuO4 is taken up as an example for chiral superconductivity. Here the vortex state in the mixed state in each superconductor is focused on from the view point of their unconventionality.

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  • Collective modes of incommensurate spin density wave in one-dimensional Hubbard model

    M Ichioka, E Kaneshita, K Machida

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   70 ( 3 )   818 - 828   2001.3

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    Dynamical spin and charge susceptibility and collective modes are studied in the framework of the random phase approximation. They are calculated from the wave function of the selfconsistently obtained ground state, including all possible higher harmonics components of the ordering vector Q. We investigate a spin wave excitation in the spin transverse mode, and phason excitation related to the domain-wall motion in the spin longitudinal and charge modes. We consider the dispersion curve of the collective mode, and discuss the dependence on the on-site U interaction and the period of the incommensurate structure.

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  • Spin and charge excitations in incommensurate spin density waves

    E Kaneshita, M Ichioka, K Machida

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   70 ( 3 )   866 - 876   2001.3

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    Dynamical longitudinal spin susceptibility X-zz(q,w) and charge density susceptibility X-nn(q,w) are evaluated within random phase approximation for incommensurate spin density waves, or stripes, in two dimensional Hubbard model. Taking into account all possible higher harmonics of the fundamental component of the order parameter,we calculate these quantities for the full ranges of the momentum and energy, and analyze collective modes related to the motion of the stripe line. The anisotropy of the dispersion cone comes from the moving pattern of the stripes, i.e., the compression mode or the meandering mode. In the metallic stripe, there are also nesting excitations of the parallel sheet of the Fermi surfaces. We also discuss the excitation of the silent position in the insulating stripe.

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  • Vortex structure in superconducting stripe states

    M Ichioka, M Takigawa, K Machida

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   70 ( 1 )   33 - 36   2001.1

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    The vortex structure in superconducting stripe states is studied according to the Bogoliubov-de Gennes theory on the two-dimensional Hubbard model with nearest-neighbor sites pairing interaction. The vortex is trapped at the outside region of the stripe line, where the superconductivity is weak. The superconducting coherence length along the stripe direction becomes long. There are no eminent low-energy electronic states even near the vortex core. These characters resemble the Josephson vortex in layered superconductors under a parallel field.

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  • Static and Dynamical Properties of Stripes in Underdoped Cuprates

    Kazushige Machida, Masanori Ichioka, Eiji Kaneshita

    Journal of the Physical Society of Japan, Suppl. A   2001

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  • Site-selective nuclear magnetic relaxation time in a superconducting vortex state

    M Takigawa, M Ichioka, K Machida

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   69 ( 12 )   3943 - 3954   2000.12

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    On the basis of the microscopic Bogoliubov-de Gennes theory, the dependence of the nuclear spin relaxation time T-1 around vortices on the temperature and field is studied comparatively for both s-wave superconductor and d-wave superconductor. Reflecting low energy electronic excitations associated with the vortex core, the dependence of T-1 on the site and temperature deviate from those of the zero-field case, and T-1 becomes faster with approaching the vortex core. In the core region, T-1(-1) has a new peak below the superconducting transition temperature T-c. The dependence of the overall T-1(T) on the field for s-wave and d-wave superconductors is investigated and analyzed in terms of the local density of states. The NMR study by the dependence of T-1 on the resonance field may be a new method to probe the spatial resolved vortex core structure in various conventional and unconventional superconductors.

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  • Quasiparticle structure of stripes in high T-c cuprates

    M Ichioka, K Machida

    PHYSICA B-CONDENSED MATTER   281   804 - 805   2000.6

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    We investigate the metallic stripe state by the self-consistent mean-field theory of the Hubbard model, focusing on La2-xSrxCuO4. We consider the band dispersion, the local density of states and the spectral weight to clarify the contribution of the mid-gap states. The superconducting state formed by quasiparticles of the stripe state is also studied. (C) 2000 Elsevier Science B.V. All rights reserved.

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  • Electronic structure of stripes in two-dimensional Hubbard model

    M Ichioka, K Machida

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   68 ( 12 )   4020 - 4031   1999.12

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    Focusing on La2-xSrxCuO4, me study the stripe structure by the self-consistent mean-field theory of the Hubbard model. By introducing the realistic Fermi surface topology, the SDW-gapped insulator is changed to metallic. The solitonic features of the stripe structure and the contribution of the mid-gap states are presented. We consider the band dispersion, the local density of states, the spectral weight, and the optical conductivity, associated with the solitonic structure. These results may provide important information for the experimental research of the stripe structure, such as the angle-resolved photoemission experiments. The "Fermi surface" shape is changed depending on the ratio of the incommensurability delta and the hole density n(h). In real space, only the stripe region is metallic when delta/n(h) is large.

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  • Theory of vortex excitation imaging via an NMR relaxation measurement

    M Takigawa, M Ichioka, K Machida

    PHYSICAL REVIEW LETTERS   83 ( 15 )   3057 - 3060   1999.10

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    The temperature dependence of the site-dependent nuclear spin relaxation time T-1 around vortices is studied in s-wave and d-wave superconductors. Reflecting low-energy electronic excitations associated with the vortex core, temperature dependences deviate from those of the zero-field case, and T-1 becomes faster when approaching the vortex core. In the core region, T-1(-1) has a new peak below T-c. The NMR study by the resonance field dependence may be a new method to prove the spatial resolved vortex core structure in various superconductors.

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  • Field dependence of the vortex structure in d-wave and s-wave superconductors

    M Ichioka, A Hasegawa, K Machida

    JOURNAL OF SUPERCONDUCTIVITY   12 ( 4 )   571 - 574   1999.8

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    The vortex structure and its field dependence are studied in the clean limit on the basis of the quasi-classical Eilenberger theory to find their difference between d(x2-y2)- and s-wave pairings. We show the d(x2-y2)-wave nature and the vortex lattice effect on the local density of states around the vortex, and on the field dependence of the spatially averaged density of states. The d(x2-y2)-wave pairing introduces a fourfold symmetric structure around each vortex core in the pair potential and the internal held. With increasing field, their contribution becomes significant to the whole structure of the vortex lattice state.

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  • Stripe structure, spectral feature and soliton gap in high T-c cuprates

    K Machida, M Ichioka

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   68 ( 7 )   2168 - 2171   1999.7

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    We show that lightly doped La2-xSrxCuO4 can be described in terms of a stripe magnetic structure or soliton picture. The internal relationship between the recent neutron observation of the diagonal (x=0.05) to vertical (x greater than or equal to 0.06) stripe transition, which was predicted, and the concomitant metal-insulator transition, is clarified by soliton physics. The phase diagram with the unidentified transition lines between the antiferromagnetic and stripe phases, the doping dependence of the modulation period, and the origin of the mid-infrared optical absorption are investigated and compared with other single-layer systems, La2-xSrxNiO4 and (La, Nd)(2-x)SrxCuO4. A novel type of quasi-particles and holes is fully responsible for metallic conduction and ultimately superconductivity.

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  • Field dependence of the vortex structure in d-wave and s-wave superconductors

    M Ichioka, A Hasegawa, K Machida

    PHYSICAL REVIEW B   59 ( 13 )   8902 - 8916   1999.4

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    We study the vortex structure and its field dependence within the framework of the quasiclassical Eilenberger theory to find the difference between the d(x2-y2-) and s-wave pairings. We clarify the effect of the d(x2-y2)-wave nature and the vortex lattice effect on the vortex structure of the pair potential, the internal field and the local density of states. The d(x2-y2)-wave pairing introduces a fourfold-symmetric structure around each vortex core. With increasing field, their contribution becomes significant to the whole structure of the vortex lattice state, depending on the vortex lattice's configuration. It is reflected in the form factor of the internal field, which may be detected by small-angle neutron scattering, or the resonance line shape of muon spin resonance and NMR experiments. We also study the induced s- and d(xy)-wave components around the vortex in d(x2-y2)-wave superconductors. [S0163-1829(99)02213-4].

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  • Vortex lattice effects on low-energy excitations in d-wave and s-wave superconductors

    M Ichioka, A Hasegawa, K Machida

    PHYSICAL REVIEW B   59 ( 1 )   184 - 187   1999.1

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    Generic features of the low-energy excitations in the vortex lattice state are examined by comparatively studying the self-consistent solutions of the quasiclassical Eilenberger theory both for d(x2)-(y2)-wave and s-wave pairings. This low-energy physics associated with a vortex core, nodal structure, and quasiparticle transfer between vortices governs physical properties of the vortex such as the field dependences of the zero-energy density of states, the internal field distribution, and the shrinkage of the core radius. Eminent differences between two pairings an highlighted to help analyze experimental data. [S0163-1829(99)00102-2].

    DOI: 10.1103/PhysRevB.59.184

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  • Relation between vortex core charge and vortex bound states

    N Hayashi, M Ichioka, K Machida

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   67 ( 10 )   3368 - 3371   1998.10

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    Spatially inhomogeneous electron distribution around a single vortex is discussed on the basis of the Bogoliubov-de Gennes theory. The spatial structure and temperature dependence of the electron density around the vortex are presented. A relation between the vortex core charge and the vortex bound states (or the Caroli-de Gennes-Matricon states) is pointed out. Using the scanning tunneling microscope: information on the vortex core charge can he extracted through this relation.

    DOI: 10.1143/JPSJ.67.3368

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  • On the fourfold symmetry of H-c2 and magnetization of d(x(2)-y(2))-wave superconductors for the in-plane magnetic fields

    T Sugiyama, M Ichioka

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   67 ( 5 )   1738 - 1747   1998.5

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    For the d(x2-y2) superconductors, we investigate the foul-fold symmetry of the upper critical fields and magnetization related to the torque under the parallel magnetic field to the ab plane of the crystal. We take into account the s-wave order parameter induced from the spatial variation of the d(x2-y2)-wave order parameter. In addition, we investigate the effects of the shape of the Fermi surface. If the pairing interaction for the s-wave channel is attractive. the s-wave component can enhance the above fourfold symmetry. Depending on the structure of the Fermi surface, the fourfold symmetric anisotropy in the ab plane enhances or suppresses the fourfold symmetric behavior. There is also the case where the fourfold symmetric anisotropy of in the ab plane changes the sign of the fourfold symmetric behavior from that of the isotropic case.

    DOI: 10.1143/JPSJ.67.1738

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  • Low-lying quasiparticle excitations around a vortex core in quantum limit

    N Hayashi, T Isoshima, M Ichioka, K Machida

    PHYSICAL REVIEW LETTERS   80 ( 13 )   2921 - 2924   1998.3

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    Focusing on a quantum-limit behavior, we study a single vortex in a clean s-wave type-II superconductor by self-consistently solving the Bogoliubov-de Gennes equation. The discrete energy levels of the vortex bound states in the quantum limit are discussed. The vortex core radius shrinks monotonically up to an atomic-scale length on lowering the temperature T, and the shrinkage stops to saturate at a lower T. The pair potential, supercurrent, and local density of states around the vortex exhibit Friedel-like oscillations. The local density of states has particle-hole asymmetry induced by the vortex. These are potentially observed directly by scanning tunneling microscopy.

    DOI: 10.1103/PhysRevLett.80.2921

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  • Vortex lattice structure in a d(x(2)-y(2))-wave superconductor

    M Ichioka, N Enomoto, K Machida

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   66 ( 12 )   3928 - 3943   1997.12

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    The vortex lattice structure in a d(x2-y2)-wave superconductor is investigated near the upper critical magnetic field in the framework of the Ginzburg Landau theory extended by including the correction terms such as the higher order derivatives derived from the Gor'kov equation. On lowering temperature, the unit cell shape of the vortex lattice gradually varies from a regular triangular lattice to a square lattice through the shape of an isosceles triangle. As for the orientation of the vortex lattice, the base of an isosceles triangle is along the a axis or the b axis of the crystal. The fourfold symmetric structure around a vortex core is also studied in the vortex lattice case. It is noted that these characteristic features appear even in the case the induced s-wave order parameter is absent around the vortex of the d(x2-y2)-wave superconductivity. We also investigate the effect of the induced s-wave order parameter. It enhances (suppresses) these characteristic features of the d(x2-y2)-wave superconductor when the s-wave component of the interaction is attractive (repulsive).

    DOI: 10.1143/JPSJ.66.3928

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  • Quasiparticle spectra around a single vortex in a d-wave superconductor - Comment Reviewed

    M Franz, M Ichioka

    PHYSICAL REVIEW LETTERS   79 ( 22 )   4513 - 4513   1997.12

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    DOI: 10.1103/PhysRevLett.79.4513

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  • Local density of states in the vortex lattice in a type-II superconductor

    M Ichioka, N Hayashi, K Machida

    PHYSICAL REVIEW B   55 ( 10 )   6565 - 6576   1997.3

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    The local density of states (LDOS) in the triangular vortex lattice is investigated based on quasiclassical Eilenberger theory. We consider the case of an isotropic s-wave superconductor with the material parameter appropriate to NbSe2. At a weak magnetic field, the spatial Variation of the LDOS shows a cylindrical structure around a vortex core. On the other hand, at a high field where the core regions substantially overlap each other, the LDOS is a sixfold star-shaped structure due to the vortex lattice effect. The orientation of the star coincides with the experimental data of scanning tunneling microscopy. That is, the ray of the star extends toward the nearest-neighbor (next-nearest-neighbor) vortex direction at higher (lower) energy.

    DOI: 10.1103/PhysRevB.55.6565

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  • Ginzburg Landau theory for d-wave pairing and fourfold symmetric vortex core structure

    N Enomoto, M Ichioka, K Machida

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   66 ( 1 )   204 - 214   1997.1

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    The Ginzburg Landau theory for d(x2-y2)-wave superconductors is constructed, by starting from the Gor'kov equation with including correction terms up to the next order of ln(T-c/T). Some of the non-local correction terms are found to break the cylindrical symmetry and lead to the fourfold symmetric core structure, reflecting the internal degree of freedom in the pair potential. Using this extended Ginzburg Landau theory, we investigate the fourfold symmetric structure of the pair potential, current and magnetic field around an isolated single vortex, and clarify concretely how the vortex core structure deviates from the cylindrical symmetry in the d(x2-y2)-wave superconductors.

    DOI: 10.1143/JPSJ.66.204

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  • Effects of gap anisotropy upon the electronic structure around a superconducting vortex Reviewed

    Nobuhiko Hayashi, Masanori Ichioka, Kazushige Machida

    Physical Review B - Condensed Matter and Materials Physics   56 ( 14 )   9052 - 9063   1997

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    An isolated single vortex is considered within the framework of the quasiclassical theory. The local density of states around a vortex is calculated in a clean type-II superconductor with an anisotropy. The anisotropy of a superconducting energy gap is crucial for bound states around a vortex. A characteristic structure of the local density of states, observed in the layered hexagonal superconductor (Formula presented)-NbSe(Formula presented) by scanning tunneling microscopy (STM), is well reproduced if one assumes an anisotropic (Formula presented)-wave gap in the hexagonal plane. The local density of states (or the bound states) around the vortex is interpreted in terms of quasiparticle trajectories to facilitate an understanding of the rich electronic structure observed in STM experiments. It is pointed out that further fine structures and extra peaks in the local density of states should be observed by STM. © 1997 The American Physical Society.

    DOI: 10.1103/PhysRevB.56.9052

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  • Star-shaped local density of states around vortices in a type-II superconductor

    N Hayashi, M Ichioka, K Machida

    PHYSICAL REVIEW LETTERS   77 ( 19 )   4074 - 4077   1996.11

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    The electronic structure of vortices in a type II superconductor is analyzed within the quasiclassical Eilenberger framework. The possible origin of a sixfold ''star'' shape of the local density of states, observed by scanning tunneling microscope (STM) experiments on NbSe2, is examined in the light of the three effects: the anisotropic pairing, the vortex lattice, and the anisotropic density of states at the Fermi surface. Outstanding features of split parallel rays of this star are well explained in terms of an anisotropic s-wave pairing. This reveals not only a rich internal electronic structure associated with a vortex core, but also unique ability of the STM spectroscopy.

    DOI: 10.1103/PhysRevLett.77.4074

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  • Vortex structure in d-wave superconductors

    M Ichioka, N Hayashi, N Enomoto, K Machida

    PHYSICAL REVIEW B   53 ( 22 )   15316 - 15326   1996.6

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    The vortex structure of pure d(x2-y2)-wave superconductors is microscopically analyzed in the framework of the quasiclassical Eilenberger equations. A self-consistent solution for the d-wave pair potential is obtained in the case of an isolated vortex. The vortex core structure, i.e., the pair potential, the supercurrent, and the magnetic field, is found to be fourfold symmetric even in the case that the mixing of the s-wave component is absent. The detailed temperature dependences of these quantities are calculated. The fourfold symmetry becomes clear when the temperature is decreased. The local density of states is calculated for the self-consistently obtained pair potential. From the results, we discuss the flow trajectory of the quasiparticles around a vortex, which is characteristic in d(x2-y2)-wave superconductors. The experimental relevance of our results to high-temperature superconductors is also given.

    DOI: 10.1103/PhysRevB.53.15316

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  • Vortex core structure and possible pairing mixture in d-wave superconductors Reviewed

    K Machida, M Ichioka, N Hayashi, N Enomoto

    PHYSICA C   263 ( 1-4 )   428 - 430   1996.5

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    The vortex core structure in a d-wave superconductor is analyzed by solving the quasi-classical Eilenberger equation self-consistently. The pair function, current and magnetic field distributions around an isolated vortex are found to break circular symmetry and show four-fold symmetry, reflecting the internal degrees of freedom in d-wave pairing.

    DOI: 10.1016/0921-4534(95)00823-3

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  • 31a-PS-78 Vortex structure in d-wave superconductivity

    Hayashi N., Ichioka M., Enomoto N., Machida K.

    Abstracts of the meeting of the Physical Society of Japan. Annual meeting   51 ( 3 )   360 - 360   1996.3

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  • s- and d(xy)-wave components induced around a vortex in d(x(2)-y(2))-wave superconductors

    M Ichioka, N Enomoto, N Hayashi, K Machida

    PHYSICAL REVIEW B   53 ( 5 )   2233 - 2236   1996.2

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    The vortex structure of d(x2-y2)-wave superconductors is microscopically analyzed in the framework of the quasiclassical Eilenberger equations. If the pairing interaction contains an s-wave (d(xy)-wave) component in addition to a d(x2-y2)-wave component, the s-wave (d(xy)-wave) component of the order parameter is necessarily induced around a vortex in d(x2-y2)-wave superconductors. The spatial distribution of the induced s-wave and d(xy)-wave components is calculated. The s-wave component has an opposite winding number around the vortex near the d(x2-y2)-vortex core and its amplitude has the shape of a four-lobe clover. These are consistent with results based on the Ginzburg-Landau (GL) theory. The amplitude of the d(xy) component has the shape of an octofoil. The mixing of the d(xy) component cannot be explained by the GL theory, unless nonlocal correction terms are included.

    DOI: 10.1103/PhysRevB.53.2233

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  • S- and-wave components induced around a vortex in-wave superconductors Reviewed

    M. Ichioka, N. Enomoto, N. Hayashi, K. Machida

    Physical Review B - Condensed Matter and Materials Physics   53 ( 5 )   2233 - 2236   1996

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    The vortex structure of (Formula presented)-wave superconductors is microscopically analyzed in the framework of the quasiclassical Eilenberger equations. If the pairing interaction contains an s-wave ((Formula presented)-wave) component in addition to a (Formula presented)-wave component, the s-wave ((Formula presented)-wave) component of the order parameter is necessarily induced around a vortex in (Formula presented)-wave superconductors. The spatial distribution of the induced s-wave and (Formula presented)-wave components is calculated. The s-wave component has an opposite winding number around the vortex near the (Formula presented)-vortex core and its amplitude has the shape of a four-lobe clover. These are consistent with results based on the Ginzburg-Landau (GL) theory. The amplitude of the (Formula presented) component has the shape of an octofoil. The mixing of the (Formula presented) component cannot be explained by the GL theory, unless nonlocal correction terms are included. © 1996 The American Physical Society.

    DOI: 10.1103/PhysRevB.53.2233

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  • VORTEX LATTICE OF LAYERED SUPERCONDUCTORS IN PARALLEL MAGNETIC-FIELDS

    M ICHIOKA

    PHYSICAL REVIEW B   51 ( 14 )   9423 - 9426   1995.4

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    DOI: 10.1103/PhysRevB.51.9423

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  • Fundamental properties of a vortex in a d-wave superconductor

    M Ichioka, N Hayashi, N Enomoto, K Machida

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   64 ( 12 )   4547 - 4551   1995

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    The vortex core structure in a d-wave superconductor is analyzed on the basis of the quasi-classical Eilenberger theory beyond the Ginzburg-Landau framework. The current and magnetic field distributions around an isolated vortex break the circular symmetry observed in s-wave pairing and show fourfold symmetry, reflecting, the internal degrees of freedom in d-wave pairing, i.e., (k) over cap(x)(2) - (k) over cap(y)(2) in reciprocal space through the low lying quasi-particle excitations. The peculiar orientation of the flux line lattice observed recently in a cuprate is discussed in light of the present theory.

    DOI: 10.1143/JPSJ.64.4547

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Books

  • 「超伝導磁束状態の物理」 (分担執筆)

    市岡優典( Role: Joint author ,  2.8 渦糸電子状態と異方的超伝導)

    裳華房  2017.4  ( ISBN:9784785329228

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    Responsible for pages:pp.127-134   Language:Japanese

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  • Superconductivity - Theory and Applications "jointly worked"

    ( Role: Joint author)

    2011  ( ISBN:9789533071510

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  • Topology in Ordered Phases

    K. Machida, *M. Ichioka, H. Adachi, T. Mizushima, N. Nakai, and P. Miranovic(Microscopic Structure of Vortices in Type II Superconductors)

    World Scientific Publishing, Singapore  2006 

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  • Ruthenate and Rutheno-Cuprate Materials ---Unconventional Superconductivity, Magnetism and Quantum Phase Transitions--- [Lecture Notes in Physics VOL. 603]

    edited by C. Noce, A. Vecchione, M. Cuoco, A. Romano(Unconventional Superconductivity with Either Multi-component or Multi-band, or with Chirality)

    Springer-Verlag Berlin Heidelberg  2002 

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    Responsible for pages:p.32 - 45  

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  • Vortices in Unconventional Superconductors and Superfluids [Springer Series in Solid-State Sciences. VOL. 132]

    edited by R.P. Huebener, N. Schopohl, G.E. Volovik(13. Magnetic Field Dependence of the Vortex Structure Based on the Microscopic Theory)

    Springer, Heidelberg  2002 

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    Responsible for pages:p.225 - 242  

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  • Chapter 13. Vortex Structure in Clean Type(]G0002[) Superconductors with s-wave and d-wave Pair Symmetries "jointly worked"

    "The superconducting state in magnetic fields" World Scientific, Singapore 

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Presentations

  • ネマティック超伝導での二回対称な渦芯状態の理論評価

    市岡 優典

    基研研究会「非自明な電子状態が生み出す超伝導現象の最前線:新たな挑戦と展望」 

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    Event date: 2021.12.22 - 2021.12.24

    Language:Japanese   Presentation type:Poster presentation  

    Venue:京都大学基礎物理学研究所(京都)& オンライン  

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  • ネマティック超伝導体の渦糸状態での 非磁性不純物効果

    市岡優典, 世良泰明, 上田貴裕, 安立裕人

    日本物理学会2021年秋季大会  日本物理学会

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    Event date: 2021.9.20 - 2021.9.23

    Language:Japanese   Presentation type:Oral presentation (general)  

    Venue:オンラライン  

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  • NON-MAGNETIC IMPURITY EFFECTS IN VORTEX STATES OF NEMATIC SUPERCONDUCTOR International conference

    Masanori IchiokaYasuaki SeraTakahiro, UedaHiroto Adachi

    18th Online International Vortex Conference 2021 (Vortex 2021) 

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    Event date: 2021.5.27 - 2021.6.4

    Language:English   Presentation type:Poster presentation  

    Venue:Online: Indian Institute of Technology Kanpur (IIT Kanpur), Kanpur, Uttar Pradesh and Tata Institute of Fundamental Research (TIFR), Mumbai  

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  • カイラル超伝導体の渦糸状態での不純物散乱効果の理論研究

    市岡優典, 上田貴裕, 世良泰明, 安立裕人

    基研研究会「高温超伝導・非従来型超伝導研究の最前線:多様性と普遍性」  京都大学基礎物理学研究所

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    Event date: 2020.10.26 - 2020.10.28

    Language:Japanese   Presentation type:Poster presentation  

    Venue:オンライン  

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  • 傾斜磁場下の表面近くでの渦糸状態

    市岡優典

    第27回渦糸物理ワークショップ 

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    Event date: 2019.12.17 - 2019.12.19

    Language:Japanese   Presentation type:Oral presentation (general)  

    Venue:京都大学理学研究科セミナーハウス(京都)  

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  • 傾斜磁場での表面近くの超伝導渦糸状態

    市岡優典

    基研研究会「電子相関が生み出す超伝導現象の未解決問題と新しい潮流」 

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    Event date: 2019.10.28 - 2019.10.30

    Presentation type:Poster presentation  

    Venue:京都大学基礎物理学研究所(京都)  

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  • Local NMR Relaxation Rates T1-1 and T2-1 in the Vortex State of Chiral and Helical P-Wave Superconductors International conference

    M. Ichioka, K.K. Tanaka, S. Onari

    International Conference on Strongly Correlated Electron Systems 2019 

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    Event date: 2019.9.23 - 2019.9.28

    Language:English   Presentation type:Poster presentation  

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  • Local electronic states around a vortex near the surface for inclined magnetic fields Invited International conference

    M. Ichioka

    XVII International Workshop on Vortex Matter in Superconductors (VORTEX 2019) 

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    Event date: 2019.9.23 - 2019.9.28

    Language:English   Presentation type:Oral presentation (invited, special)  

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  • 傾斜磁場下の表面近くでの渦糸まわりの局所電子状態2

    市岡優典

    日本物理学会 2019年秋季大会  日本物理学会

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    Event date: 2019.9.10 - 2019.9.13

    Language:Japanese   Presentation type:Oral presentation (general)  

    Venue:岐阜大学(岐阜)  

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  • 非従来型超伝導と渦糸周りの局所電子状態

    市岡優典

    渦のコスモロジー研究会 

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    Event date: 2019.6.1 - 2019.6.2

    Language:Japanese   Presentation type:Oral presentation (general)  

    Venue:大阪府立大学(堺)  

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  • 面内磁場回転での低温比熱振動における非磁性不純物効果

    市岡優典, 橋谷侑希, 田中健太

    日本物理学会 2018年秋季大会  日本物理学会

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    Event date: 2018.9.9 - 2018.9.12

    Language:Japanese   Presentation type:Oral presentation (general)  

    Venue:同志社大学(京田辺)  

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  • D-vector Dependence of Local NMR Relaxation Rates T1-1 and T2-1 in the Vortex State of Chiral and Helical P-wave Superconductors International conference

    M. Ichioka, K.K. Tanaka, S. Onari

    12th International Conference on Materials and Mechanisms of Superconductivity (M2S-HTSC-XII) 

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    Event date: 2018.8.19 - 2018.8.24

    Language:English   Presentation type:Poster presentation  

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  • Eilenberger理論による磁場を傾けた場合の渦糸状態

    市岡優典

    超伝導とその周辺:渦糸物理と検出器の新展開 

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    Event date: 2018.6.8 - 2018.6.9

    Language:Japanese   Presentation type:Oral presentation (general)  

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  • カイラルp波超伝導の渦状態における局所核磁気緩和率のdベクトル依存性

    市岡優典, 田中健太, 大成誠一郎

    基研研究会「電子相関が生み出す新規な秩序と超伝導現象:トポロジー、液晶状態、動的現象」 

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    Event date: 2018.5.7 - 2018.5.9

    Language:Japanese   Presentation type:Poster presentation  

    Venue:京都大学基礎物理学研究所(京都)  

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  • 傾斜磁場下の表面近くでの渦糸まわりの局所電子状態

    市岡優典

    日本物理学会 第73回年次大会  日本物理学会

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    Event date: 2018.3.22 - 2018.3.25

    Language:Japanese   Presentation type:Oral presentation (general)  

    Venue:東京理科大学(野田)  

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  • 傾斜磁場下の表面近くの渦糸状態

    第25回渦糸物理国内会議 -超伝導体における渦糸状態の物理と応用(2017)-  2017 

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  • 2バンド超伝導体におけるバンド毎の渦糸芯半径の磁場温度依存性

    日本物理学会 第72回年次大会  2017 

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  • 趣旨説明(シンポジウム「超伝導スピントロニクスの物理とその展望」)

    日本物理学会 2017年秋季大会  2017 

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  • Paramagnetic and Diamagnetic Pair-Breaking Effect in Electric-Field-Induced Surface Superconductivity under Parallel Magnetic Fields

    29th International Symposium on Superconductivity (ISS2016)  2016 

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  • 2バンド超伝導体におけるバンド毎の渦糸半径

    第24回渦糸物理国内会議 -超伝導体における渦糸状態の物理と応用(2016)-  2016 

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  • Transverse Components of Flux Line Lattice Form Factors in Uniaxial Superconductors

    28th International Symposium on Superconductivity (ISS2015)  2015 

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  • 磁束線構造因子の磁場方位依存性:Eilenberger理論とLondon理論の比較

    日本物理学会第70回年次大会  2015 

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  • 磁束線格子構造因子の横磁場成分の準古典理論評価

    金研共同利用ワークショップ「超伝導体における渦糸状態の物理と応用(2013)」  2013 

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  • Vortex States for Nearly B//ab in a Chiral p-Wave Superconductor

    The International Conference on Strongly Correlated Electron Systtems (SCES2013)  2013 

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  • カイラルp波超伝導の面内磁場での渦糸状態の準古典理論評価

    日本物理学会2013年秋季大会  2013 

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  • 渦糸格子構造因子横磁場成分の準古典理論評価

    日本物理学会第68回年次大会  2013 

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  • 趣旨説明 (シンポジウム「超伝導位相制御:量子化・ダイナミクスの物理と応用展開」にて)

    日本物理学会第68回年次大会  2013 

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  • Vortex states in a two-band superconductor MgB2 based on Eilenberger theory

    CECAM workshop "Novel Phenomena in Multi-Condensate Superconductors, Superfluids, and Ultracold Gases”  2012 

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  • Local electronic states in electric-field induced surface superconductivity

    International Symposium on Physics and Chemistry of Novel Superconductors and Related Materials  2012 

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  • 磁束格子形状のフェルミ面異方性効果のEilenberger理論評価

    第20回渦糸物理国内会議  2012 

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  • 2バンド超伝導体でのHc1近くの渦糸状態

    日本物理学会 第67回年次大会  2012 

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  • 2バンド超伝導体のHc1近くの渦状態

    第19回渦糸物理国内会議  2011 

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  • 電場誘起表面超伝導での局所電子状態の理論評価

    新学術領域「対称性の破れた凝縮系におけるトポロジカル量子現象」第2回領域研究会  2011 

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  • Vortex Structure in Chiral p-wave Superconductors Studied by Eilenberger Theory

    6th International Conference on Low Temperature Physics (LT26)  2011 

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  • カイラルp波超伝導体での渦格子構造と磁束線構造因子

    日本物理学会2011年秋季大会  2011 

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  • 渦糸状態における不純物効果の準古典理論評価

    第18回磁束線物理国内会議  2010 

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  • カイラルp波超伝導体での渦格子状態

    新学術領域研究「対称性の破れた凝縮系におけるトポロジカル量子現象」第1回領域研究会  2010 

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  • d波超伝導の渦糸状態における不純物効果の準古典理論評価

    日本物理学会2010年秋季大会  2010 

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  • Flux line lattice form factor studied by Eilenberger theory

    The 12th International Workshop on Vortex Matter in Superconductors  2009 

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  • d波超伝導体の面内磁場での磁束格子構造

    日本物理学会第64回年次大会  2009 

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  • 大きなパウリ常磁性効果をもつd波超伝導体における渦糸格子構造

    日本物理学会第64回年次大会  2009 

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  • 渦糸格子変形における一次相転移の理論

    第17回磁束線物理国内会議 (VPWJ2009)  2009 

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  • 超流動ヘリウム3渦状態についての準古典理論計算

    スーパークリーン特定・A04班2009年度研究発表会  2009 

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  • FFLO状態の磁場変化についての準古典理論計算

    日本物理学会2009年秋季大会  2009 

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  • 準古典理論による下部臨界磁場の評価

    第17回磁束線物理国内会議 (VPWJ2009)  2009 

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  • Vortex states in superconductors with strong paramagnetic effects

    “New Developments in Theory of Superconductivity” Symposium  2009 

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  • Textures and exotic vortices in neutral Fermi superfluids

    International Symposium on Quantum Fluids and Solids 2009 (QFS2009)  2009 

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  • p波超流動体に潜むマヨラナ型準粒子励起

    スーパークリーン特定・A03, A04班合同研究会  2009 

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  • 渦糸状態での常磁性効果

    スーパークリーン特定・A03, A04班合同研究会  2009 

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  • 第2種超伝導体における渦糸格子構造の配向の1次相転移の理論

    日本物理学会2009年秋季大会  2009 

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  • Vortex Lattice Transformation in d-wave Superconductors with Pauli Paramagnetic Effect

    9th International Conference on Materials and Mechanisms of Superconductivity (M2S-IX Tokyo 2009)  2009 

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  • Flux line lattice form factor and paramagnetic effects in type II superconductors

    25th International Conference on Low Temperature Physics (LT25)  2008 

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  • 磁束状態の中性子散乱強度と常磁性効果

    日本物理学会2008年秋季大会  2008 

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  • Mermin-Ho渦格子状態についての準古典理論計算

    日本物理学会第63回年次大会  2008 

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  • FFLOと渦糸状態における常磁性効果と電子状態

    基研研究会「不均一超伝導超流動状態と量子物理」  2008 

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  • d波超伝導体の面内磁場での磁束格子構造

    第16回渦糸物理国内会議  2008 

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  • Vortex states in spin-triplet superconductors based on quasi-classical theory

    スーパークリーン特定・研究成果報告会 '08  2008 

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  • URu2Si2の磁場中比熱の理論研究

    日本物理学会 2007年春期大会  2007 

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  • Quantized Vortices and Majorana Zero Modes in Anisotropic Fermi Superfluid under p-wave Feshbach Resonance

    International Symposium on Physics of New Quantum Phases in Superclean Materials (PSM2007)  2007 

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  • 磁束渦糸状態における常磁性効果

    第15 回渦糸物理国内会議  2007 

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  • Vortex states in superconductors with strong Pauli-paramagnetic effect

    The 4th CREST Nano-Virtual-Labs Joint Workshop on Superconductivity: Critical Currents(NVLS2007-CC)  2007 

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  • The unconventional vortex structure in p-wave superfluid

    International Symposium on Physics of New Quantum Phases in Superclean Materials (PSM2007)  2007 

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  • Giant Vortices in Fermi Gases near a Feshbach Resonance: Cases with and without Population Imbalance

    International Symposium on Physics of New Quantum Phases in Superclean Materials (PSM2007)  2007 

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  • カイラルp波超伝導でのリトル・パークス振動

    日本物理学会・第62回年次大会  2007 

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  • p波フェッシュバッハ共鳴を有するフェルミ超流動体の量子渦構造とマヨラナ粒子の存在について

    日本物理学会・第62回年次大会  2007 

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  • FFLO状態におけるトンネル効果の理論

    日本物理学会 2007年春期大会  2007 

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  • テクスチャー構造の秩序変数の超伝導状態(理論) [シンポジウム「不均一超流動・超伝導の物理」にて]

    日本物理学会・第62回年次大会  2007 

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  • p波超伝導体の特殊な渦糸構造

    日本物理学会・第62回年次大会  2007 

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  • Vortex structure in p-wave superconductors based on quasiclassical theory

    International Symposium on Physics of New Quantum Phases in Superclean Materials (PSM2007)  2007 

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  • BCS-BECクロスオーバー領域における粒子数不均衡な超流動状態

    日本物理学会 2007年春期大会  2007 

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  • Suppression of superconductivity at high fields in Sr2RuO4

    特定領域研究「スーパークリーン物質で実現する新しい量子相の物理」A04スピン三重項超伝導小研究会  2006 

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  • 空間反転対称性のない超伝導のマイスナー状態と磁束渦糸状態

    日本物理学会 2006年秋季大会 (千葉大学)  2006 

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  • 超伝導混合状態での準粒子熱伝導率

    日本物理学会 2006年秋季大会 (千葉大学)  2006 

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  • VORTEX STATE IN A FFLO SUPERCONDUCTOR

    The 17th International Conference on Magnetism (ICM2006)  2006 

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  • 粒子数不均衡なフェルミ超流動体における量子渦構造

    日本物理学会 2006年秋季大会 (千葉大学)  2006 

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  • 磁束渦糸状態における常磁性効果とFFLO状態

    特定領域研究”100テスラ領域の強磁場スピン科学”第3回シンポジウム  2006 

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  • 磁束渦糸状態での常磁性効果と中性子小角散乱強度

    日本物理学会 2006年秋季大会 (千葉大学)  2006 

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  • s波超伝導体の渦糸格子状態に対する核磁気緩和率の研究

    日本物理学会 2006年秋季大会 (千葉大学)  2006 

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  • Vortex States in a Spin-Triplet Pairing Superconductor

    特定領域研究「スーパークリーン物質で実現する新しい量子相の物理」A03&A04研究項目合同ワークショップ  2006 

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  • Vortex structure and the electronic state in FFLO superconductors

    The Vth Symposium on New Trends of Physics ‐Physics of Novel Superconductivity–  2006 

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  • 渦糸周りの低励起構造と走査トンネル顕微鏡のスペクトル

    日本物理学会 第61回年次大会(愛媛大学・松山大学)  2006 

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  • Vortex States in Superconductors with Large Pauli-Paramagnetic Effect

    特定領域研究「スーパークリーン物質で実現する新しい量子相の物理」研究成果報告会  2006 

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  • 準古典理論によるFFLO磁束渦糸状態での電子構造

    日本物理学会 第61回年次大会(愛媛大学・松山大学)  2006 

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  • 超伝導混合状態での準粒子熱伝導率

    日本物理学会 第61回年次大会(愛媛大学・松山大学)  2006 

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  • 空間反転対称性のない超伝導の渦糸構造

    日本物理学会 第61回年次大会(愛媛大学・松山大学)  2006 

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  • 擬1次元有機超伝導体のペア対称性と核磁気緩和率II

    日本物理学会 第61回年次大会(愛媛大学・松山大学)  2006 

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  • 中性フェルミ気体におけるパウリ極限での超流動状態

    日本物理学会 第61回年次大会(愛媛大学・松山大学)  2006 

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  • パウリリミットに近い超伝導体の渦糸電子状態

    日本物理学会第60回年次大会(東京理科大学野田キャンパス)  2005 

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  • 超流動フェルミ原子気体におけるFFLO状態とその渦構造

    日本物理学会第60回年次大会(東京理科大学野田キャンパス)  2005 

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  • 非従来型超伝導体における異方的反磁性応答II

    日本物理学会2005年秋季大会 (同志社大学京田辺キャンパス)  2005 

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  • 中井宣之,P.Miranovic,*市岡優典,町田一成

    日本物理学会2005年秋季大会 (同志社大学京田辺キャンパス)  2005 

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  • Electronic Aspects of Vortices in Type II Superconductors

    International Conference Vortex IV  2005 

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  • 磁束渦糸状態におけるパウリ常磁性効果とナイトシフト

    日本物理学会2005年秋季大会 (同志社大学京田辺キャンパス)  2005 

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  • Electronic structure of vortex in a FFLO superconductor

    18th International Symposium on Superconductivity (ISS2005)  2005 

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  • Magnetization Process in a Chiral p-wave Superconductor with Multi-domains

    特定領域研究「スーパークリーン物質で実現する新しい量子相の物理」領域発足研究会  2005 

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  • 擬1次元有機超伝導体のペア対称性と核磁気緩和率

    日本物理学会2005年秋季大会 (同志社大学京田辺キャンパス)  2005 

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  • Fulde-Ferrell-Larkin-Ovchinnikov状態における渦糸構造

    日本物理学会2005年秋季大会 (同志社大学京田辺キャンパス)  2005 

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  • Fulde-Ferrell-Larkin-Ovchinnikov states in Fermi gases with unequal populations

    24th International Conference on Low Temperature Physics (LT24)  2005 

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  • Spatially Modulated Superfluid Phases in Fermion Systems with Unequal Atomic Populations

    14th INTERNATIONAL LASER PHYSICS WORKSHOP 2005 (LPHYS'05)  2005 

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  • Electronic structure of vortex in the FFLO superconducting state

    24th International Conference on Low Temperature Physics (LT24)  2005 

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  • Electronic states around vortex in a Fulde-Ferrell-Larkin-Ovchinnikov superconductor

    CREST Nano-Virtual-Labs Joint Workshop on Superconductivity (CREST-NVLS-2005)  2005 

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  • 中井宣之,P.Miranovic,市岡優典・町田一成

    東北大学金属材料研究所ワークショップ「超伝導体における渦糸状態の物理と応用」  2005 

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  • 擬1次元有機超伝導体の渦糸構造と核磁気緩和率

    東北大学金属材料研究所ワークショップ「超伝導体における渦糸状態の物理と応用」  2005 

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  • 磁束渦糸状態におけるパウリ常磁性効果とナイトシフト

    東北大学金属材料研究所ワークショップ「超伝導体における渦糸状態の物理と応用」  2005 

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  • 非従来型超伝導体における異方的反磁性応答

    東北大学金属材料研究所ワークショップ「超伝導体における渦糸状態の物理と応用」  2005 

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  • Electronic Structure of Vortex State in a FFLO Superconductor

    特定領域研究「スーパークリーン物質で実現する新しい量子相の物理」領域発足研究会  2005 

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  • Microscopic structure of vortices in superconductors

    the first international symposium on Topology in Ordered Phases (TOP2005)  2005 

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  • MgB_2_での磁束渦糸の電子状態

    日本物理学会第60回年次大会(東京理科大学野田キャンパス)  2005 

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  • 多成分超伝導体での磁束渦糸状態と磁束の流れ

    科研費特定領域研究「充填スクッテルダイト構造に創出する新しい量子多電子状態の展開」第3回研究会  2005 

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  • 渦糸格子状態の内部磁場構造に対する異方的超伝導ギャップの影響

    日本物理学会第60回年次大会(東京理科大学野田キャンパス)  2005 

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  • カイラルp波超伝導体の不純物まわりの電子状態

    日本物理学会第60回年次大会(東京理科大学野田キャンパス)  2005 

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  • Vortex and Domain structure in a chiral p wave superconductor

    Kyoto International Symposium on Spin-Triplet Superconductivity and Ruthenate Physics [STSR2004]  2004 

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  • Vortex core structure in high Tc superconductor

    第17回国際超電導シンポジウム(ISS2004)  2004 

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  • 多バンド超伝導体のギャップ構造と渦糸格子の回転

    日本物理学会 2004年秋季大会  2004 

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  • Electronic state around vortex in a two-band superconductor

    Joint Workshop on Superconductivity The Second CREST-NANOFAB Workshop (NFS2004) The XII-th Vortex Physics Workshop of Japan (VPJ12) Progress in nanoscopic superconductors and vortex physics  2004 

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  • 渦糸周りの準粒子状態に対するラインノードとフルギャップによる違いに関する理論研究

    日本物理学会 第59回年次大会  2004 

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  • 反強磁性を伴った渦糸格子状態における熱伝導率

    日本物理学会 第59回年次大会  2004 

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  • PrOs4Sb12の渦糸状態について2

    日本物理学会 第59回年次大会  2004 

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  • 非従来型超伝導体の異方的反磁性応答

    日本物理学会 2004年秋季大会  2004 

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  • 高温超伝導体のチェッカーボード構造と電子状態

    日本物理学会 2004年秋季大会  2004 

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  • Double Transition and Vortex Sheet Structure in Multi-Component Superconductors

    THE INTERNATIONAL CONFERENCE ON STRONGLY CORRELATED ELECTRON SYSTEMS (SCES '04)  2004 

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  • 超流動フェルミ原子気体におけるFFLO状態の可能性

    日本物理学会 2004年秋季大会  2004 

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  • PrOs4Sb12の超伝導での渦糸状態について

    特定領域研究「充填スクッテルダイト構造に創出する新しい量子多電子状態の展開」第一回研究会  2003 

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  • Zero energy density of states in superconductors with gap nodes

    日本物理学会第58回年次大会  2003 

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  • 反強磁性渦糸芯の準粒子状態と核磁気緩和率III

    日本物理学会第58回年次大会  2003 

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  • 異方的超伝導体における渦糸格子の回転に対する安定性

    日本物理学会2003年秋季大会  2003 

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  • PrOs4Sb12の渦糸状態について

    日本物理学会2003年秋季大会  2003 

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  • 斜めストライプ領域の spectral weight

    日本物理学会第58回年次大会  2003 

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  • Beliaev Damping of Transverse Quadrupole Modes in Single-Vortex Bose-Einstein Condensates

    12th INTERNATIONAL LASER PHYSICS WORKSHOP 2003 (LPHYS'03)  2003 

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  • 光格子でのBECの不安定性

    日本物理学会第58回年次大会  2003 

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  • Bose凝縮体における渦糸状態の集団励起とBeliaev減衰

    日本物理学会第58回年次大会  2003 

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  • 異方的超伝導体における磁束格子と準粒子状態の構造

    日本物理学会第58回年次大会  2003 

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  • 2バンド超伝導体の渦糸電子状態

    磁束線物理国内会議  2003 

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  • Vortex state in unconventional superconductors

    第6回日米先端科学(JAFoS)シンポジウム2003  2003 

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  • Domain wall and vortex structure in unconventional superconductors

    JST-CREST: The First NANOFAB Workshop “Theoretical developments of nanosuperconductors and its applications”  2003 

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  • 反強磁性渦糸芯の準粒子状態と核磁気緩和率

    日本物理学会 第57回年次大会  2002 

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  • 超伝導磁束渦糸状態の微視的理論計算

    ISSP Theory Forum for the 21 Century  2002 

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  • p波超伝導体での渦糸構造の磁場依存性 2

    日本物理学会 第57回年次大会  2002 

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  • Field Dependence of Electronic Specific Heat in MgB_2

    科研費特定領域研究(A)「遷移金属酸化物における新しい量子現象」成果報告会  2002 

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  • Phonon Anomalies due to Collective Stripe Modes in High Tc Cuprates

    科研費特定領域研究(A)「遷移金属酸化物における新しい量子現象」成果報告会  2002 

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  • カイラルp波超伝導体の磁化過程

    日本物理学会 2002年秋季大会(中部大学)  2002 

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  • 超伝導ストライプ状態での局所状態密度

    日本物理学会 2002年秋季大会 (中部大学)  2002 

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  • カイラルp波超伝導体の磁化過程

    東北大学金属材料研究所研究会「超伝導体における渦糸状態の物理 --- 統一的理解に向けて---」  2002 

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  • 反強磁性渦糸芯の準粒子状態と核磁気緩和率II

    日本物理学会 2002年秋季大会 (中部大学)  2002 

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  • 四回対称の異方性を持つ超伝導体における渦糸格子構造

    日本物理学会 2002年秋季大会 (中部大学)  2002 

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  • Study of Phonon Anomalies in Stripe phase of High Tc Cuprates

    The 23rd International Conference on Low Temperature Physics (広島国際会議場)  2002 

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  • Multiple components of the order parameter induced around the d_{x^2-y^2}-wave vortex core

    The 23rd International Conference on Low Temperature Physics (広島国際会議場)  2002 

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  • 反強磁性渦糸芯の準粒子状態と核磁気緩和率

    日本物理学会 第57回年次大会  2002 

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  • Microscopic study of low-κ type-II superconductors

    The 23rd International Conference on Low Temperature Physics (広島国際会議場)  2002 

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  • Theoretical Study on Vortex Lattices in Tetragonal Superconductors

    The 23rd International Conference on Low Temperature Physics (広島国際会議場)  2002 

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  • Field dependence of vortex structure in p_x ± i p_y -wave superconductor

    The 23rd International Conference on Low Temperature Physics (広島国際会議場)  2002 

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  • 異方的超伝導体における渦糸格子と準粒子状態の構造

    東北大学金属材料研究所研究会「超伝導体における渦糸状態の物理 --- 統一的理解に向けて---」  2002 

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  • 拡張ハバードモデルによる反強磁性を伴った渦糸構造

    東北大学金属材料研究所研究会「超伝導体における渦糸状態の物理 --- 統一的理解に向けて---」  2002 

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  • p波超伝導体での渦糸構造の磁場依存性 2

    日本物理学会 第57回年次大会  2002 

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  • 超伝導ギャップの異方性と渦糸格子構造

    日本物理学会 第57回年次大会  2002 

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  • 超伝導ギャップの異方性と渦糸格子構造

    日本物理学会 第57回年次大会  2002 

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  • Thermal Conductivity in the Vortex Lattice of d-wave and s-wave Superconductors

    The JST International Symposium on Superconducting Device Physics  2001 

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  • 擬一次元ハロゲン架橋複核金属錯体のソリトン

    日本物理学会 第2001年秋季大会  2001 

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  • カイラルp波超伝導の対称性と渦糸構造

    日本物理学会 第2001年秋季大会  2001 

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  • Vortex Structure in p-wave Superconductors based on Tight-Binding Model

    The JST International Symposium on Superconducting Device Physics  2001 

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  • YNi_2 B_2 Cにおけるフォノン異常と超伝導ギャップ異方性

    日本物理学会 第2001年秋季大会  2001 

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  • p波超伝導体での渦糸構造の磁場依存性

    日本物理学会 第2001年秋季大会  2001 

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  • 渦糸格子状態における熱伝導率

    日本物理学会 第56回年次大会  2001 

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  • Vortex Structure in Sr_2RuO_4

    ISSP国際シンポジウム"Correlated Electrons"  2001 

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  • 渦糸格子状態における熱伝導率II

    日本物理学会 第2001年秋季大会  2001 

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  • 多バンド超伝導体の渦糸格子における電子状態

    日本物理学会 第2001年秋季大会  2001 

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  • Dynamical Properties of stripes

    ISSP国際シンポジウム"Correlated Electrons"  2001 

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  • 渦糸格子状態の局所状態密度と熱伝導率

    物性研短期研究会・ 「高温超伝導体におけるボルテックス・マターの物理」  2001 

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  • ストライプ中のフォノン異常

    日本物理学会 第2001年秋季大会  2001 

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  • ストライプ相の集団励起2

    日本物理学会第55回年次大会  2000 

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  • 二次元ハバードモデルでのストライプ相の電子状態と集団励起

    科学技術庁マルチコアプロジェクト基礎理論動向調査ワーキンググループ研究会 『ストライプ構造と擬ギャップ及び磁束状態と超伝導層間結合』  2000 

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  • Magnetic field dependence of the vortex structure in the quasiclassical theory

    INTERNATIONAL WORKSHOP ON "Microscopic Structure and Dynamics of Vorticed in Unconventional Superconductors and Superfluids"  2000 

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  • 渦糸まわりの準粒子状態と核磁気緩和率の磁場による変化

    日本物理学会2000年春の分科会  2000 

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  • ストライプ相の集団励起

    日本物理学会2000年春の分科会  2000 

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  • 渦糸まわりの準粒子状態と核磁気緩和率

    日本物理学会 中国四国支部 2000年支部例会  2000 

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  • 低ドープ域でのストライプ構造

    日本物理学会第54回年会  1999 

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  • 渦糸まわりの準粒子状態の核磁気緩和率への寄与

    東北大学金属材料研究所共同利用研究会・戦略的基礎ミニシンポジウム『高温超伝導体における渦糸状態』  1999 

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  • 渦糸状態での核磁気緩和の理論

    日本物理学会1999年秋の分科会  1999 

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  • ハバードモデルによるストライプとその電子状態

    日本物理学会1999年秋の分科会  1999 

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  • Quasiparticle structure of stripes in high Tc cuprates

    The LI-st Yamada Conference on "STRONGLY CORRELATED ELECTRON SYSTEMS"  1999 

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  • ストライプがある時の超伝導・渦糸状態

    日本物理学会1999年秋の分科会  1999 

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  • 低ドープ域での不整合磁気秩序と準粒子励起構造

    日本物理学会第54回年会 低温シンポジウム(なぜ,高温超伝導体でストライプなのか?)  1999 

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  • 2次元ハバードモデルでのストライプ状態の電子構造

    第6回田中シンポジウム『高温超伝導体の電荷秩序』  1999 

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Awards

  • 科学研究費補助金第一段審査における模範審査意見に対する表彰

    2009  

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    Country:Japan

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Research Projects

  • Theoretical study of vortex states and superconducting properties in multi-orbital electronic system

    Grant number:21K03471  2021.04 - 2025.03

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)  Grant-in-Aid for Scientific Research (C)

    市岡 優典

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    Grant amount:\4160000 ( Direct expense: \3200000 、 Indirect expense:\960000 )

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  • Physics of Spin-triplet superconductivity

    Grant number:19H00657  2019.04 - 2023.03

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (A)  Grant-in-Aid for Scientific Research (A)

    鄭 国慶, 俣野 和明, 川崎 慎司, 市岡 優典

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    Grant amount:\44590000 ( Direct expense: \34300000 、 Indirect expense:\10290000 )

    2019年度において、以下の成果を得た。
    1)遷移金属Crを含む化合物A2Cr3As3(A=Na,K,Rb)において、超伝導ギャップに普遍的に点状のノード(ギャップがゼロ)が存在することを明らかにした。また、この物質群が強磁性量子臨界点付近に位置し、量子臨界点への距離はアルカリ金属Aの半径によって制御できることを発見した。Aの半径が大きいほど、A-Cr-Aのボンド角が90度に近づき、強磁性相互作用を増大させることを指摘した。これらの結果はA2Cr3As3が超流動ヘリウムの固体版であることを示唆している。
    2)トポロジカル絶縁体Bi2Se3にCuをドープする単結晶を作製し、Cu濃度が広範囲にわたる高品質な超伝導試料を得た。Se-NMRを測定した結果、Cu濃度が類似した試料において、スピン三重項超伝導を記述するdベクトルが90度異なることがあるのを発見した。この結果は、dベクトルは局所的なひずみによってピン止めされることを示唆する。また、Cu濃度が0.4を超えると、超伝導ギャップが異方的(nematic)なものから等方的なものに変わることを発見した。これは、高ドープ域ではカイラル超伝導状態が実現している可能性が高いことを示すものである。
    3)空間反転対称性の破れた超伝導体TaRh2B2を作製し、NMR測定を行った。その結果、非従来型超伝導状態が実現していること、常伝導状態では電子相関の強いことが明らかになった。
    4)非磁性不純物効果と超伝導ギャップ対称性の対応関係を理論的に明らかにした。

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  • Theoretical study of vortex states to clarify the mechanism of superconductors having significant spin-orbit coupling

    Grant number:17K05542  2017.04 - 2021.03

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)  Grant-in-Aid for Scientific Research (C)

    市岡 優典

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    Grant amount:\4680000 ( Direct expense: \3600000 、 Indirect expense:\1080000 )

    本研究では、非従来型超伝導やスピン軌道相互作用に関係した超伝導機構を解明するため、第一原理電子状態計算より得られた情報も利用し、磁場中の渦糸状態の空間構造や物性を定量的に正しく計算する手法を開発している。これまで、第一原理電子状態計算の情報をもとに多軌道系電子状態のモデルを構成し、スピン軌道相互作用を導入して、クーパー対を形成する擬スピンの基底でフェルミ面上の軌道角運動量とスピン角運動量の情報を得る手法の開発した。そして、その擬スピンの基底におけるクーパー対としてスピン一重項超伝導の場合やスピン三重項超伝導の場合での磁場中物性について理論研究を進めている。超伝導体Sr2RuO4に注目した研究では、超伝導臨界磁場の評価に加え、臨界温度以下の温度での超伝導状態におけるスピンや軌道の分極などを評価する研究に取り組んでいる。
    磁場方位が様々な場合での渦糸状態の物性の研究も進めている。磁場方向をc軸から傾けた場合の渦糸電子状態の理論計算では、表面近くでの渦糸線の曲がり方の理論評価が可能なことを示し、走査型トンネル顕微鏡(STM)で観測される渦糸像の磁場角度依存性を解明するなど、渦糸がある場合の表面での理論計算手法を、ほぼ確立することができた。渦糸状態での非磁性不純物散乱効果の理論評価の研究では、d波超伝導体において面内で磁場を回転させた場合での低温比熱の振動現象における不純物散乱効果の評価や、2回対称性を持つ超伝導ギャップの場合の不純物散乱効果の研究を行った。後者の2回対称性を持つ超伝導の研究では、異方的s波とスピン三重項p波の超伝導対称性の場合を比較して、渦糸周りの超伝導秩序変数や局所電子状態の空間構造を比べることにより、渦糸状態における不純物散乱効果と超伝導対称性の関係を明らかにした。

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  • Theoretical study of local electronic states and physical properties in electric-field-induced surface superconductivity

    Grant number:25400373  2013.04 - 2017.03

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)  Grant-in-Aid for Scientific Research (C)

    Ichioka Masanori, ONARI Seiichiro, TANAKA Kenta, NABETA Masahiro, Kogan Vladimir, Schmalian Jörg

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    Grant amount:\5200000 ( Direct expense: \4000000 、 Indirect expense:\1200000 )

    Spatial structures of the local superconductivity and the bound electronic state near the surface are theoretically studied based on calculations of the Bogoliubov-de Gennes equation, focusing electric-field-induced surface superconductivity. Especially, in the pair-breaking effect by magnetic fields parallel to the surface, new mechanism by the diamagnetic effect is considered in addition to the paramagnetic effect. From the results, it is clarified that contributions by the sub-band structure and multi-gap superconductivity eminently appear in the magnetic field dependence of the superconductivity.

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  • Novel Physics of non-centrosymmetric superconductors

    Grant number:20244058  2008 - 2011

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (A)  Grant-in-Aid for Scientific Research (A)

    ZHENG Guo-qing, INADA Yoshihiko, KAWASAKI Shinji, ICHIOKA Masanori, SAKURAI Yoshiharu

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    Grant amount:\47320000 ( Direct expense: \36400000 、 Indirect expense:\10920000 )

    We have grown polycrystal samples of non-centrosymmetric superconductors Li_2(Pt_<1-x> Pd_x)_3B and studied the evolution of the superconducting state by NMR. We found that the superconducting state changes abruptly at x~ 0. 8. By analyzing the crystal structure, we found that the Pt(Pd) B_6 tilts abruptly beyond x~ 0. 8, which enhances the spin-orbit coupling and is responsible for the change in the superconducting state properties. We have also studied other non-centrosymmetric superconductors such as Mg_10Ir_19B_16 and Re_7B_3. The results also suggest that the local structure distortion is effective in enhancing the degree of inversion symmetry-breaking.

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  • 微視的理論によるスピン三重項超伝導・超流動での特異な渦状態についての解明

    Grant number:20029016  2008 - 2009

    日本学術振興会  科学研究費助成事業 特定領域研究  特定領域研究

    市岡 優典, 町田 一成, 水島 健

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    Grant amount:\2300000 ( Direct expense: \2300000 )

    冷却原子気体で実現が期待されているスピン三重項p波超流動に注目し、ヘリウム3の等方的p波超流動やルテニウム酸化物のカイラルp波超伝導との関連も視野に入れて、秩序変数に内部自由度のあるp波超流動状態での渦状態について理論研究を行ってきた。特に、原子気体でのp波超流動は研究の萌芽期にあり、今後の実験観測でどのような渦状態が現れるかの理論予測を早期に行い、今後の実験研究のための指針となるような成果を心がけ研究を進めた。ヘリウム3超流動においては秩序変数の内部自由度の多彩さのためマーミン・ホー渦のように渦芯のないトポロジカルな構造の渦が実現している。それらの特異な渦の構造を微視的理論などにより詳細に解析し、冷却原子気体を含むp波超伝導・超流動の渦状態の特性を総合的に解明してきた。
    内部自由度のあるp波超伝導・超流動の渦状態の空間構造や関係する物理量の計算を可能とするための計算手法として、現象論的手法であるギンツブルグ・ランダウ理論による計算方法、定量的に正しい微視的理論による評価をするための準古典理論やボゴリュウボブ・ドジャン理論による計算方法の開発を行なった。これにより、ヘリウム3で実現しているマーミン・ホー渦やカイラルp波超伝導での渦と類似の渦構造が冷却原子気体で実現する可能性を評価し、その空間構造を理論計節より明らかにした。特に、マヨラナ状態として注目されるp波超伝導量子渦での準粒子状態の存在と特性の解明を行った。また、d波対状態など、より高次の角運動量状態の場合にも研究を発展させ、その特異な渦状態の理論解析を行なった。この他、本特定領域研究に参加している実験グループとの情報交換を行い、ヘリウム3超流動の回転下での特異な渦状態や、ルテニウム酸化物・重い電子系などでの特異な超伝導状態に関しても研究を進めている。

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  • Theoretical study for quantitative estimate for properties of vortex states, and extension to multi-component superconductors

    Grant number:19540369  2007 - 2010

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)  Grant-in-Aid for Scientific Research (C)

    ICHIOKA Masanori

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    Grant amount:\4290000 ( Direct expense: \3300000 、 Indirect expense:\990000 )

    Spatial structure of vortex states in unconventional superconductors was theoretically studied, in order to establish theoretical methods to quantitatively estimate the temperature and magnetic field dependence of physical quantities, such as specific heat, magnetization, small angle neutron scattering intensity, and NMR spectrum. Using these, we extract information about mechanisms of unconventional superconductivity. The numerical methods to calculate vortex states in multicomponent superconductors, including spin-triplet pairing, were also developed.

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  • スピン3重項超伝導体におけるスピン流の理論的研究

    Grant number:18043001  2006 - 2007

    日本学術振興会  科学研究費助成事業 特定領域研究  特定領域研究

    浅野 泰寛, 市岡 優典

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    Grant amount:\2000000 ( Direct expense: \2000000 )

    本研究課題ではスピン3重項超伝導体に固有の輸送現象の解明を目指している.18年度はその中でもスピン・ジョセフソン効果の基本的な性質の解明と,観測に向けての提案を行った.超スピン流に関する研究はヘリウム3ですでに行われているが,本研究ではスピン3重項超伝導体Sr_2RuO_4を念頭に超スピン流を制御しながら流すための理論的提案を行った.超伝導体中のクーパー対はスピンの外に電荷の自由度をもち,電荷が電磁場とゲージ結合するためスピン流の制御が可能になるという結論を得た.スピン流の基礎的性質の研究とその応用研究は現在磁性体を用いた微小素子においてきわめて盛んに行われており,デバイス応用の可能性も高くなってきた.その意味で超伝導体を用いたスピン流の研究はとても時宜を得たものと考えられる.
    19年度はT字形状の超伝導体と常伝導体の接合の電気伝導測定から,スピン1重項超伝導体と3重項超伝導体の峻別が可能であることを示した.この目的のためには多くの実験があるが,ルテニウム酸化物をはじめとして多くの3重項超伝導体について,スピン3重項超伝導を否定する意見もないわけではない.こうした状況の下で,超伝導の対称性をはっきりと区別できる方法の提案は,この分野の発展に大きく寄与すると考えられる.

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  • 磁束渦糸状態から探る非従来型超伝導体の物性

    Grant number:16740202  2004 - 2006

    日本学術振興会  科学研究費助成事業 若手研究(B)  若手研究(B)

    市岡 優典

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    Grant amount:\3100000 ( Direct expense: \3100000 )

    重い電子系などの超伝導磁束渦糸状態の物性を理解する上でパウリ常磁性効果による超伝導対破壊の効果をきちんと考慮に入れて計算する必要がある。このため今年度は、超伝導異方性に加え、パウリ常磁性効果による対破壊効果も考慮した磁束渦糸状態の理論計算を行い、磁束渦糸状態の空間構造、磁場依存性・温度依存性におけるパウリ常磁性効果の影響を超伝導異方性の効果とともに明らかにする研究を行った。磁束渦糸状態での常磁性効果が実際の超伝導体で現れていることを検証するため、常磁性帯磁率や磁化の磁場変化などの基本的な物理量に加え、NMRのスペクトルや中性子散乱強度などの物理量を計算することにより、どのように常磁性効果が現れるべきかを解明する計算を実施し、CeCoIn_5やTmNi_2B_2Cなどの実験データを例にして常磁性効果の大きさが評価できることを示した。これらの成果は論文投稿準備中である。また、パウリ常磁性効果と関連した興味深い超伝導状態として、CeCoIn_5で発見されたFFLO(Fulde-Ferrell-Larkin-Ovchinikov)状態についても、NMRスペクトルなどの実験に対応した微視的理論計算を行い、その磁場温度依存性などFFLO磁束渦糸状態の性質について議論した。
    一方、多成分超伝導オーダーパラメーターの系における特異な磁束渦糸状態の静的・動的性質についてのシミュレーション研究も、引き続き実施している。今年度は、非磁性不純物の周りの自発電流の空間構造や、ナノ構造超伝導体での超伝導空間構造・磁束渦糸構造に注目し、その中で、多成分超伝導体であることによる特異な振舞いを明らかにする研究を行った。特に、超伝導体に穴を開けてリング状にした系を考え、オーダーパラメーターの空間構造の磁場変化や転移温度の振舞いなど、多成分超伝導体でのリトルパークス効果の特異な様子を確かめる研究を進めている。

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  • 高温超伝導体の渦糸構造についての理論的研究

    Grant number:96J05484  1998

    日本学術振興会  科学研究費助成事業 特別研究員奨励費  特別研究員奨励費

    市岡 優典

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    Grant amount:\1200000 ( Direct expense: \1200000 )

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Class subject in charge

  • Modern Physics for General Education (Quantum mechanics) (2021academic year) 1st semester  - 金5~6

  • Basic Mathematical and Data Sciences (2021academic year) Third semester  - 月3~4

  • Materials Physics I (2021academic year) Prophase  - 月1,月2

  • Quantum Mechanics 1A (2021academic year) Third semester  - 木1,木2

  • Quantum Mechanics 1B (2021academic year) Fourth semester  - 木1,木2

  • Quantum Mechanics 2A (2021academic year) 1st semester  - 火1,火2

  • Quantum Mechanics 2B (2021academic year) Second semester  - 火1,火2

  • Quantum Many-Body Physics (2021academic year) Late  - その他

  • Seminar in Quantum Many-Body Physics (2021academic year) Year-round  - その他

  • Introduction to Interdisciplinary Science 1 (2020academic year) Prophase  - 水1,水2

  • Modern Physics for General Education (Quantum mechanics) (2020academic year) 1st semester  - 金5,金6

  • Basic Mathematical and Data Sciences (2020academic year) Third semester  - 月3,月4

  • Mathematical Data Sciences(Basics of Machine Learning) (2020academic year) special  - その他

  • Materials Physics I (2020academic year) Prophase  - 月1,月2

  • Philosophy and ethics in the science (2020academic year) Year-round  - その他

  • Quantum Mechanics 1A (2020academic year) Third semester  - 木1,木2

  • Quantum Mechanics 1B (2020academic year) Fourth semester  - 木1,木2

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  • Quantum Mechanics 2 (2020academic year) 1st and 2nd semester  - 火5,火6

  • Quantum Many-Body Physics (2020academic year) Late  - その他

  • Seminar in Quantum Many-Body Physics (2020academic year) Year-round  - その他

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