研究者詳細 - 市岡　優典

論文 - 市岡　優典

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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年7月

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

Masahiro Ishihara, Yuujirou Amano, Masanori Ichioka, Kazushige Machida

PHYSICAL REVIEW B 87 ( 22 ) 2013年6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

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.

DOI： 10.1103/PhysRevB.87.224509

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

Tomoya Hirano, Kenta Takamori, Masanori Ichioka, Kazushige Machida

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 82 ( 6 ) 063708-1-063708-4 2013年6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：PHYSICAL SOC JAPAN

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.

DOI： 10.7566/JPSJ.82.063708

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

Masaki Ishikawa, Yasumasa Tsutsumi, Masanori Ichioka, Kazushige Machida

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 82 ( 4 ) 2013年4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：PHYSICAL SOC JAPAN

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.

DOI： 10.7566/JPSJ.82.043711

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

Yousuke Mizohata, Masanori Ichioka, Kazushige Machida

PHYSICAL REVIEW B 87 ( 1 ) 2013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

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

DOI： 10.1103/PhysRevB.87.014505

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

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：PHYSICAL SOC JAPAN

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

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

Takeshi Daino, Masanori Ichioka, Takeshi Mizushima, Yukio Tanaka

PHYSICAL REVIEW B 86 ( 6 ) 2012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

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.

DOI： 10.1103/PhysRevB.86.064512

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

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

PHYSICAL REVIEW B 85 ( 6 ) 2012年2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

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).

DOI： 10.1103/PhysRevB.85.060505

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

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

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

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：IOP PUBLISHING LTD

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

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

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

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

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：IOP PUBLISHING LTD

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.

DOI： 10.1088/1742-6596/400/1/012051

Vortex States of Chiral p-wave Superconductors 査読

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

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

担当区分：筆頭著者記述言語：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：IOP PUBLISHING LTD

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.

DOI： 10.1088/1742-6596/400/2/022031

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

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

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 80 ( 12 ) 2011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：PHYSICAL SOC JAPAN

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.

DOI： 10.1143/JPSJ.80.123706

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

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

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 80 ( 11 ) 2011年11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：PHYSICAL SOC JAPAN

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.

DOI： 10.1143/JPSJ.80.113702

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

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：PERGAMON-ELSEVIER SCIENCE LTD

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.

DOI： 10.1016/j.jpcs.2010.10.038

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

Kenta M. Suzuki, Masanori Ichioka, Kazushige Machida

PHYSICAL REVIEW B 83 ( 14 ) 2011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

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.

DOI： 10.1103/PhysRevB.83.140503

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

Y. Tsutsumi, M. Ichioka, K. Machida

PHYSICAL REVIEW B 83 ( 9 ) 2011年3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

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.

DOI： 10.1103/PhysRevB.83.094510

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

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

JOURNAL OF LOW TEMPERATURE PHYSICS 162 ( 3-4 ) 196 - 203 2011年2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：SPRINGER/PLENUM PUBLISHERS

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.

DOI： 10.1007/s10909-010-0313-1

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

Takanobu Akiyama, Masanori Ichioka, Kazushige Machida

JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 80 ( 1 ) 2011年1月

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

Kenta M. Suzuki, Masanori Ichioka, Kazushige Machida

PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS 470 S564 - S565 2010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：ELSEVIER SCIENCE BV

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.

DOI： 10.1016/j.physc.2009.11.081

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

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：ELSEVIER

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.

DOI： 10.1016/j.physc.2009.11.174

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