研究者詳細 - 市岡　優典

論文 - 市岡　優典

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Fractional Vortex Array Realized at Twin Boundary in a Nematic Superconductor 査読

Sakiko Noda, Hiroto Adachi, Masanori Ichioka

Journal of the Physical Society of Japan 2025年2月

Time-dependent Ginzburg-Landau theory of the vortex spin Hall effect 査読

Hiroto Adachi, Yusuke Kato, Jun-ichiro Ohe, Masanori Ichioka

Physical Review B 2024年5月

Supercurrent distribution in real-space and anomalous paramagnetic response in a superconducting quasicrystal 査読

Takumi Fukushima, Nayuta Takemori, Shiro Sakai, Masanori Ichioka, Anuradha Jagannathan

Physical Review Research 2023年11月

Supercurrent Distribution on Ammann-Beenker Structure 査読

Takumi Fukushima, Nayuta Takemori, Shiro Sakai, Masanori Ichioka, Anuradha Jagannathan

Journal of Physics: Conference Series 2461 ( 1 ) 2023年

掲載種別：研究論文（国際会議プロシーディングス）

We study the distribution of supercurrent in the attractive Hubbard model on a periodic approximant of the Ammann-Beenker structure by means of the Bogoliubov-de Gennes (BdG) mean-field theory. We first investigate the spatial distributions of the electron density and superconducting order parameter and find a crossover between superconducting states with (i) extended, (ii) localized, and (iii) short-ranged Cooper pairs, similar to the previous results on the Penrose tiling. Furthermore, we formulate the expression of the supercurrent for the periodic approximant in terms of the eigenenergies and the wave functions of the Bogoliubov-de Gennes Hamiltonian and numerically investigate how the local supercurrent distribution varies by changing the direction of the applied phase gradient.

DOI： 10.1088/1742-6596/2461/1/012014

Evidence for a Square-Square Vortex Lattice Transition in a High- Tc Cuprate Superconductor 査読

D. J. Campbell, M. Frachet, S. Benhabib, I. Gilmutdinov, C. Proust, T. Kurosawa, N. Momono, M. Oda, M. Horio, K. Kramer, J. Chang, M. Ichioka, D. Leboeuf

Physical Review Letters 129 ( 6 ) 2022年8月

掲載種別：研究論文（学術雑誌）

Using sound velocity and attenuation measurements in high magnetic fields, we identify a new transition in the vortex lattice state of La2-xSrxCuO4. The transition, observed in magnetic fields exceeding 35 T and temperatures far below zero field Tc, is detected in the compression modulus of the vortex lattice, at a doping level of x=p=0.17. Our theoretical analysis based on Eilenberger's theory of the vortex lattice shows that the transition corresponds to the long-sought 45° rotation of the square vortex lattice, predicted to occur in d-wave superconductors near a van Hove singularity.

DOI： 10.1103/PhysRevLett.129.067001

Antiferromagnetic spin Seebeck effect across the spin-flop transition: A stochastic Ginzburg-Landau simulation

Yutaka Yamamoto, Masanori Ichioka, Hiroto Adachi

Physical Review B 105 ( 10 ) 2022年3月

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

Takuya Taira, Yusuke Kato, Masanori Ichioka, Hiroto Adachi

PHYSICAL REVIEW B 103 ( 13 ) 2021年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：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

Nonmagnetic impurity effect in vortex states of chiral superconductors 査読

Takahiro Ueda, Yasuaki Sera, Hiroto Adachi, Masanori Ichioka

PHYSICAL REVIEW B 103 ( 1 ) 2021年1月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：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

Vortex Cores in Narrow Thin-Film Strips 査読

Vladimir G. Kogan, Masanori Ichioka

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 89 ( 9 ) 2020年9月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：PHYSICAL SOC JAPAN

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

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

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

PHYSICAL REVIEW B 101 ( 21 ) 2020年6月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER PHYSICAL SOC

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

Spin pumping into a spin glass material 査読

Yusei Fujimoto, Masanori Ichioka, Hiroto Adachi

PHYSICAL REVIEW B 101 ( 18 ) 2020年5月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER PHYSICAL SOC

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

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

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

PHYSICAL REVIEW B 101 ( 6 ) 2020年2月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：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

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

Yasuaki Sera, Takahiro Ueda, Hiroto Adachi, Masanori Ichioka

SYMMETRY-BASEL 12 ( 1 ) 2020年1月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：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

Spin Seebeck effect in paramagnets and antiferromagnets at elevated temperatures 査読

Yutaka Yamamoto, Masanori Ichioka, Hiroto Adachi

PHYSICAL REVIEW B 100 ( 6 ) 2019年8月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER PHYSICAL SOC

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

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

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

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 88 ( 6 ) 2019年6月

担当区分：最終著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：PHYSICAL SOC JAPAN

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

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

Takuya Taira, Masanori Ichioka, So Takei, Hiroto Adachi

PHYSICAL REVIEW B 98 ( 21 ) 2018年12月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER PHYSICAL SOC

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

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

Kenta K Tanaka, Masanori Ichioka, Seiichiro Onari

Journal of Physics: Conference Series 969 ( 1 ) 2018年4月

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：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

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 査読

Kenta K. Tanaka, Masanori Ichioka, Seiichiro Onari

Physical Review B 97 ( 13 ) 2018年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：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

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

Hiroto Adachi, Yutaka Yamamoto, Masanori Ichioka

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

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

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

PHYSICAL REVIEW B 96 ( 9 ) 296 - 303 2017年9月

担当区分：責任著者記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：AMER PHYSICAL SOC

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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