Publications (115)
Spin triplet superconductivity with line nodes in Sr2RuO4
Yasumasa Hasegawa, Kazushige Machida, Masa-aki Ozaki
Several possible odd-parity states are listed up group-theoretically and examined in light of recent experiments on SrRuO. Those include some of the -wave pairing states…
Theoretical studies for identifying horizontal line nodes via angle-resolved density of states measurements ---Application to SrRuO---
Kazushige Machida, Koki Irie, Katsuhiro Suzuki +1
On the basis of the microscopic quasi-classical Eilenberger theory, we analyze the recent angle-resolved specific heat experiment carried out at low temperature for SrRuO…
Electronic Structure of Stripes in Two-Dimensional Hubbard Model
Masanori Ichioka, Kazushige Machida
Focusing on La_{2-x}Sr_{x}CuO_{4}, we study the stripe structure by the self-consistent mean-field theory of the Hubbard model. By introducing the realistic Fermi surface topology,…
Fermi Arc of Metallic Diagonal Stripes in High Tc Cuprates
Eiji Kaneshita, Masanori Ichioka, Kazushige Machida
Spectral weight is investigated for metallic diagonal stripe state in two dimensional Hubbard model, and Fermi arc observed by angle-resolved photoemission spectroscopy on LSCO is…
Bragg spectroscopy of a cigar shaped Bose condensate in optical lattices
Tarun Kanti Ghosh, Kazushige Machida
We study properties of excited states of an array of weakly coupled quasi-two-dimensional Bose condensates by using the hydrodynamic theory. We calculate multibranch Bogoliubov-Blo…
Non-unitary triplet superconductivity tuned by field-controlled magnetization --URhGe, UCoGe and UTe--
Kazushige Machida
We report on theoretical studies on ferromagnetic superconductors, URhGe, and UCoGe and identifies the pairing state as a non-unitary spin-triplet one, analogous to superfluid …
Spin and charge excitations in incommensurate spin density waves
Eiji Kaneshita, Masanori Ichioka, Kazushige Machida
Collective excitations both for spin- and charge-channels are investigated in incommensurate spin density wave (or stripe) states on two-dimensional Hubbard model. By random phase…
Transverse magnetic field and chiral-nonchiral transition in vortex states for nearly B//ab in chiral p-wave superconductors
Masahiro Ishihara, Yuujirou Amano, Masanori Ichioka +1
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 anisot…
Eilenberger theory and London theory for transverse components of flux line lattice form factors in uniaxial superconductors
Yuujirou Amano, Masahiro Ishihara, Masanori Ichioka +2
We theoretically study the magnetic field orientation dependence of longitudinal and transverse flux line lattice form factors in uniaxial superconductors with anisotropy ratio cor…
Anomalous Field-Angle Dependence of the Specific Heat of Heavy-Fermion Superconductor UPt3
Shunichiro Kittaka, Koji An, Toshiro Sakakibara +5
We have investigated the field-angle variation of the specific heat C(H, phi, theta) of the heavy-fermion superconductor UPt3 at low temperatures T down to 50 mK, where phi and the…
Field Dependence of Electronic Specific Heat in Two-Band Superconductors
Noriyuki Nakai, Masanori Ichioka, Kazushige Machida
The vortex structure is studied in light of MgB theoretically based on a two-band superconducting model by means of Bogoliubov-de Gennes framework. The field dependence of the…
Stable Skyrmions in SU(2) Gauged Bose-Einstein Condensates
Takuto Kawakami, Takeshi Mizushima, Muneto Nitta +1
We demonstrate that the three-dimensional Skyrmion, which has remained elusive so far, spontaneously appears as the ground state of (2) symmetric Bose-Einstein condensates coup…
Quasi-Classical Calculation of the Mixed-State Thermal Conductivity in s-Wave and d-Wave Superconductors
Hiroto Adachi, Predrag Miranovic, Masanori Ichioka +1
To see how superconducting gap structures affect the longitudinal component of mixed-state thermal conductivity kappa_{xx}(B), the magnetic-field dependences of kappa_{xx}(B) in s-…
Rotation of Triangular Vortex Lattice in the Two-Band Superconductor MgB2
Tomoya Hirano, Kenta Takamori, Masanori Ichioka +1
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…
Ginzburg Landau theory for d-wave pairing and fourfold symmetric vortex core structure
Naoki Enomoto, Masanori Ichioka, Kazushige Machida
The Ginzburg Landau theory for d_{x^2-y^2}-wave superconductors is constructed, by starting from the Gor'kov equation with including correction terms up to the next order of ln(T_c…
A Spin Triplet Superconductor UPt
Yasumasa Tsutsumi, Kazushige Machida, Tetsuo Ohmi +1
Motivated by a recent angle-resolved thermal conductivity experiment that shows a twofold gap symmetry in the high-field and low-temperature C phase in the heavy-fermion supercondu…
Orientation of point nodes and nonunitary triplet pairing tuned by the easy-axis magnetization in UTe2
Shunichiro Kittaka, Yusei Shimizu, Toshiro Sakakibara +6
The gap structure of a novel uranium-based superconductor UTe, situated in the vicinity of ferromagnetic quantum criticality, has been investigated via specific-heat $C(T,H,Ω)…
Local density of states in the vortex lattice in a type II superconductor
Masanori Ichioka, Nobuhiko Hayashi, Kazushige Machida
Local density of states (LDOS) in the triangular vortex lattice is investigated based on the quasi-classical Eilenberger theory. We consider the case of an isotropic s-wave superco…
Superconducting Gap Modulation in Weak Stripe States
Masanori Ichioka, Kazushige Machida
The superconducting gap modulation is investigated in the presence of a weak stripe structure, using the Bogoliubov-de Gennes theory on the two-dimensional Hubbard model with neare…
Spin triplet nematic pairing symmetry and superconducting double transition in UThBe
Kazushige Machida
Motivated by a recent experiment on UThBe with , we develop a theory to narrow down the possible pair symmetry to consistently describe the double trans…
A simple method to create a vortex in Bose-Einstein condensate of alkali atoms
Mikio Nakahara, Tomoya Isoshima, Kazushige Machida +2
Bose-Einstein condensation in alkali atoms has materialized quite an interesting system, namely a condensate with a spin degree of freedom. In analogy with the A-phase of the super…
Topological spin texture and d-vector rotation in spin-triplet superconductors: A case of UTe2
Yasumasa Tsutsumi, Kazushige Machida
A novel spin texture formed by Cooper pair spins is found theoretically with a phase string attached by half-quantized vortices at both ends in a unit cell and characterized by its…
Vortex State and Field-Angle Resolved Specific Heat Oscillation for H // ab in d-Wave Superconductors
Masayuki Hiragi, Kenta M. Suzuki, Masanori Ichioka +1
When magnetic field is applied parallel to the ab plane in d_{x^2-y^2}-wave superconductors, the transition of stable vortex lattice structure, spatial structure of local density o…
UPt as a Topological Crystalline Superconductor
Yasumasa Tsutsumi, Masaki Ishikawa, Takuto Kawakami +4
We investigate the topological aspect of the spin-triplet -wave superconductor UPt through microscopic calculations of edge- and vortex-bound states based on the quasiclassi…
Field-Orientation Dependence of Low-Energy Quasiparticle Excitations in the Heavy-Electron Superconductor UBe13
Yusei Shimizu, Shunichiro Kittaka, Toshiro Sakakibara +5
Low-energy quasiparticle excitations in the superconducting (SC) state of UBe were studied by means of specific-heat () measurements in a rotating field. Quite unexpected…
Vortex Structure in Superconducting Stripe States
Masanori Ichioka, Mitsuaki Takigawa, Kazushige Machida
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 pairi…
Lower Critical Field Hc1(T) and Pairing Symmetry Based on Eilenberger Theory
Takanobu Akiyama, Masanori Ichioka, Kazushige Machida
We quantitatively estimate different T-dependences of Hc1 between s wave and d wave pairings by Eilenberger theory. The T-dependences of Hc1(T) show quantitative deviation from tho…
Symmetry Protected Topological Order and Spin Susceptibility in Superfluid 3He-B
Takeshi Mizushima, Masatoshi Sato, Kazushige Machida
We here demonstrate that the superfluid 3He-B under a magnetic field in a particular direction stays topological due to a discrete symmetry, that is, in a symmetry protected topolo…
Magnetization process in a chiral p-wave superconductor with multi-domains
Masanori Ichioka, Yasushi Matsunaga, Kazushige Machida
A simulation study for the magnetization process is performed for the multi-domain state in a chiral p-wave superconductor, using the time-dependent Ginzburg-Landau theory. The ext…
Fulde-Ferrell-Larkin-Ovchinnikov States in Two-Band Superconductors
Takeshi Mizushima, Masahiro Takahashi, Kazushige Machida
We examine the possible phase diagram in an - plane for Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) states in a two-band Pauli-limiting superconductor. We here demonstrate that,…
Nodal Superconductivity of UTe Probed by Field-Angle-Resolved Specific Heat on a Crystal with K
Kaito Totsuka, Yohei Kono, Yusei Shimizu +6
Field-angle-resolved specific-heat measurements were performed on a clean single crystal of a spin-triplet superconductor UTe with K and a low residual electron…
Vortex state in a Fulde-Ferrell-Larkin-Ovchinnikov superconductor based on the quasiclassical theory
Masanori Ichioka, Hiroto Adachi, Takeshi Mizushima +1
We investigate the vortex state with Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) modulations suggested for a high field phase of CeCoIn_5. On the basis of the quasiclassical Eilenberge…
Multifaceted properties of Andreev bound states: Interplay of symmetry and topology
Takeshi Mizushima, Kazushige Machida
Andreev bound states ubiquitously emerge as a consequence of nontrivial topological structures of the order parameter of superfluids and superconductors and significantly contribut…
Identification of Non-unitary triplet pairing in a heavy Fermion superconductor UPt_3
Kazushige Machida, Tetsuo Ohmi
A NMR experiment recently done by Tou et al. on a heavy Fermion superconductor UPt is interpreted in terms of a non-unitary spin-triplet pairing state which we have been advoca…
Electronic state around vortex in a two-band superconductor
Masanori Ichioka, Kazushige Machida, Noriyuki Nakai +1
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-tw…
Quantum Vortex in a Vectorial Bose-Einstein Condensate
Tomoya Isoshima, Kazushige Machida, Tetsuo Ohmi
Quantum vortices in the multi-component Bose-Einstein condensation (BEC) are investigated theoretically. It is found that three kinds of the vortex configurations are possible and…
Multiple-gap structure in electric-field-induced surface superconductivity
Yousuke Mizohata, Masanori Ichioka, Kazushige Machida
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 Bogol…
On Superconducting Double Transition in PrOs_4_Sb_12
Masanori Ichioka, Noriyuki Nakai, Kazushige Machida
Superconducting double transition in PrOs_4_Sb_12 is investigated by analyzing the anisotropy of the upper critical field H_c2 in the ab-plane, and the possible pairing state is di…
Vortex phase diagram in trapped Bose-Einstein condensation
Takeshi Mizushima, Tomoya Isoshima, Kazushige Machida
The vortex phase diagram in the external rotation frequency versus temperature is calculated for dilute Bose-Einstein condensed gases. It is determined within the Bogoliubov-Popov…
Instability of Non-vortex State toward a Quantized Vortex in Bose-Einstein Condensate under External Rotation
Tomoya Isoshima, Kazushige Machida
The instability condition of the non-vortex state toward vortex formation is exa mined within the Bogoliubov theory when a Bose-Einstein condensate is under exte rnally forced rota…
Flux flow and pinning of the vortex sheet structure in a two-component superconductor
Yasushi Matsunaga, Masanori Ichioka, Kazushige Machida
A simulation study using the time-dependent Ginzburg-Landau theory is performed for the vortex state in two-component superconductors, such as PrOs_4_Sb_12_. We investigate the flu…
Dispersive Gap Mode of Phonons in Anisotropic Superconductors
Masanori Ichioka, Kazushige Machida
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 n…
Relation between Vortex Excitation and Thermal Conductivity in Superconductors
Mitsuaki Takigawa, Masanori Ichioka, Kazushige Machida
Thermal conductivity under a field is investigated in -wave superconductors and isotropic s-wave superconductors by the linear response theory, using a mi…
Spin domain formation in spinor Bose-Einstein condensation
Tomoya Isoshima, Kazushige Machida, Tetsuo Ohmi
The spatial structure of the spinor Bose-Einstein condensates with the spin degrees of freedom is analyzed based on the generalized Gross-Pitaevskii equation (GP) in the light of t…
Spin gap and L modulated intensity at the low-energy incommensurate magnetic fluctuations in the superconducting state of Sr2RuO4
Kazuki Iida, Maiko Kofu, Katsuhiro Suzuki +11
Low-energy incommensurate (IC) magnetic fluctuations in the multiband superconductor SrRuO is investigated by high-resolution inelastic neutron scattering measurements and…
Quasi-particle evidence for the nematic state above in SrBiSe
Yue Sun, Shunichiro Kittaka, Toshiro Sakakibara +6
In the electronic nematic state, an electronic system has a lower symmetry than the crystal structure of the same system. Electronic nematic states have been observed in various un…
Collective modes of Fermi superfluid containing vortices along the BEC-BCS crossover
Tarun Kanti Ghosh, Kazushige Machida
Using the coarse-grain averaged hydrodynamic approach, we calculate all low energy transverse excitation spectrum of a rotating Fermi superfluid containing vortex lattices for all…
Symmetry protected vortex bound state in superfluid He B-phase
Yasumasa Tsutsumi, Takuto Kawakami, Ken Shiozaki +2
The superfluid He formed by spin-triplet -wave Cooper pairs is a typical topological superfluid. In the superfluid He B-phase, several kinds of vortices classified by sp…
Evidence for chiral d-wave superconductivity in URu2Si2 from the field-angle variation of its specific heat
Shunichiro Kittaka, Yusei Shimizu, Toshiro Sakakibara +7
Low-energy quasiparticle (QP) excitations in the heavy-fermion superconductor URuSi were investigated by specific-heat measurements of a high-quality sing…
Vortex states in superconductors with strong Pauli-paramagnetic effect
Masanori Ichioka, Kazushige Machida
Using the quasiclassical theory, we analyze the vortex structure of strong-paramagnetic superconductors.There, induced paramagnetic moments are accumulated exclusively around the v…
Generic First Order Orientation Transition of Vortex Lattices in Type II Superconductors
Kenta M. Suzuki, Kenji Inoue, Predrag Miranovic +2
First order transition of vortex lattices (VL) observed in various superconductors with four-fold symmetry is explained microscopically by quasi-classical Eilenberger theory combin…
Vortex lattice structure in a d_{x^2-y^2}-wave superconductor
Masanori Ichioka, Naoki Enomoto, Kazushige Machida
The vortex lattice structure in a d_{x^2-y^2}-wave superconductor is investigated near the upper critical magnetic field in the framework of the Ginzburg Landau theory extended by…
Quasiparticle heat transport in the mixed state of high superconductors
Mitsuaki Takigawa, Masanori Ichioka, Kazushige Machida
The field dependence of low-temperature thermal conductivity observed on cuprates is explained by calculating microscopically. The heat current carried by low-lying…
Theory of Ferromagnetic Superconductivity
Kazushige Machida, Tetsuo Ohmi
It is argued that the pairing symmetry realized in a ferromagnetic superconductor UGe must be a non-unitary triplet pairing. This particular state is free from the Pauli limita…
Orbital symmetry of a triplet pairing in a heavy Fermion superconductor UPt_3
Kazushige Machida, Tsutomu Nishira, Tetsuo Ohmi
The orbital symmetry of the superconducting order parameter in UPt_3 is identified by evaluating the directionally dependent thermalconductivity and ultrasound attenuation in the c…
Quasiparticle structure in antiferromagnetism around the vortex and nuclear magnetic relaxation time
Mitsuaki Takigawa, Masanori Ichioka, Kazushige Machida
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 contrib…
Microscopic Eilenberger theory of Fulde-Ferrell-Larkin-Ovchinnikov states in the presence of vortices
Kenta M. Suzuki, Kazushige Machida, Yasumasa Tsutsumi +1
We theoretically investigate the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state by using the microscopic quasi-classical Eilenberger equation. The Pauli paramagnetic effects and the…
Surface Bound States and Spontaneous Current in Cyclic d-Wave Superconductors
Masaki Ishikawa, Yasumasa Tsutsumi, Masanori Ichioka +1
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 superconductivit…
Stripe structure, spectral feature and soliton gap in high Tc cuprates
Kazushige Machida, Masanori Ichioka
We show that the lightly doped La_{2-x}Sr_{x}CuO_{4} can be described in terms of a stripe magnetic structure or soliton picture. The internal relationship between the recent neutr…
Bose-Einstein Condensation in a Confined Geometry with and without a Vortex
Tomoya Isoshima, Kazushige Machida
Various widely-used mean-field type theories for a dilute Bose gas are critically examined in the light of the recent discovery of Bose-Einstein condensation of atomic gases in a c…
Zero Energy Modes and Statistics of Vortices in Spinful Chiral p-Wave Superfluids
Takuto Kawakami, Takeshi Mizushima, Kazushige Machida
The possible stable singular vortex (SV) and half-quantum vortex (HQV) of the superfluid He-A phase confined in restricted geometries are investigated. The associated low-energ…
Symmetry Protected Topological Superfluid He-B
Takeshi Mizushima, Yasumasa Tsutsumi, Masatoshi Sato +1
Owing to the richness of symmetry and well-established knowledge on the bulk superfluidity, the superfluid He has offered a prototypical system to study intertwining of topolog…
Vortex structure in chiral p-wave superconductors
Mitsuaki Takigawa, Masanori Ichioka, Kazushige Machida +1
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 pot…
Knight shift spectrum in vortex states in s-wave and d-wave superconductors on the basis of Eilenberger theory
Kenta K. Tanaka, Masanori Ichioka, Noriyuki Nakai +1
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 the s-wave and…
Thermodynamic study of gap structure and pair-breaking effect by magnetic field in the heavy-fermion superconductor CeCu2Si2
Shunichiro Kittaka, Yuya Aoki, Yasuyuki Shimura +7
This paper presents the results of specific-heat and magnetization measurements, in particular their field-orientation dependence, on the first discovered heavy-fermion superconduc…
Excitation spectrum in a cylindrical Bose-Einstein gas
Tomoya Isoshima, Kazushige Machida
Whole excitation spectrum is calculated within the Popov approximation of the Bogoliubov theory for a cylindrical symmetric Bose-Einstein gas trapped radially by a harmonic potenti…
High-resolution magnetostriction measurements of the Pauli-limited superconductor Sr2RuO4
Shunichiro Kittaka, Yohei Kono, Toshiro Sakakibara +4
We performed high-resolution magnetostriction measurements on the Pauli-limited superconductor SrRuO using high-quality single crystals. A first-order superconducting trans…
Quasiparticle Excitations and Evidence for Superconducting Double Transitions in Monocrystalline U0.97Th0.03Be13
Yusei Shimizu, Shunichiro Kittaka, Shota Nakamura +5
Superconducting (SC) gap symmetry and magnetic response of cubic U0.97Th0.03Be13 are studied by means of high-precision heat-capacity and dc magnetization measurements using a sing…
Sharp magnetization jump at the first-order superconducting transition in Sr2RuO4
Shunichiro Kittaka, Akira Kasahara, Toshiro Sakakibara +5
The magnetization and magnetic torque of a high-quality single crystal of SrRuO have been measured down to 0.1 K under a precise control of the magnetic-field orientation.…
Symmetry Protected Topological Superfluids and Superconductors --- From the Basics to He ---
Takeshi Mizushima, Yasumasa Tsutsumi, Takuto Kawakami +3
In this article, we give a comprehensive review of recent progress in research on symmetry-protected topological superfluids and topological crystalline superconductors, and their…
Violation of the Pauli-Clogston limit in a heavy Fermion superconductor CeRhAs --Duality of itinerant and localized 4f electrons--
Kazushige Machida
We theoretically propose a mechanism to understand the violation of the Pauli-Clogston limit for the upper critical field H observed in the Ce bearing heavy Fermion mate…
Disorder-sensitive node-like small gap in FeSe
Yue Sun, Shunichiro Kittaka, Shota Nakamura +8
We investigate the band structure, nematic state and superconducting gap structure of two selected FeSe single crystals containing different amount of disorder. Transport and angle…
Interplay between effective mass anisotropy and Pauli paramagnetic effects in a multiband superconductor--Application to Sr2RuO4--
Noriyuki Nakai, Kazushige Machida
We investigate the mixed state properties in a type II multiband superconductor with uniaxial anisotropy under the Pauli paramagnetic effects. Eilenberger theory extended to a mult…
Vortex state in double transition superconductors
Yasushi Matsunaga, Masanori Ichioka, Kazushige Machida
Novel vortex phase and nature of double transition field are investigated by two-component Ginzburg-Landau theory in a situation where fourfold-twofold symmetric superconducting do…
Fully gapped superconductivity without sign reversal in the topological superconductor PbTaSe
Yue Sun, Shunichiro Kittaka, Toshiro Sakakibara +8
We investigate the superconducting gap function of topological superconductor PbTaSe. Temperature, magnetic field, and three-dimensional (3D) field-angle dependences of the spe…
Creation of persistent current and vortex in a Bose-Einstein condensate of alkali-metal atoms
Tomoya Isoshima, Mikio Nakahara, Tetsuo Ohmi +1
It is shown theoretically that a persistent current can be continuously created in a Bose-Einstein condensate (BEC) of alkali atoms confined in a multiply connected region by makin…
Novel suppression mechanism in a spin triplet superconductor -- Application to UTe--
Kazushige Machida
A novel suppression mechanism is theoretically proposed in a spin triplet superconductor (SC) with equal spin pairs. We show that the upper critical field …
Nodal gap detection through polar angle-resolved density of states measurements in uniaxial superconductors
Yasumasa Tsutsumi, Takuya Nomoto, Hiroaki Ikeda +1
We propose a spectroscopic method to identify the nodal gap structure in unconventional superconductors. This method best suits for locating the horizontal line node and for pinpoi…
Vortex Stabilization in Dilute Bose-Einstein Condensate Under Rotation
Tomoya Isoshima, Kazushige Machida
The stability of a quantized vortex state in Bose-Einstein condensation is examined within Bogoliubov theory for alkali atom gases confined in a harmonic potential under forced rot…
Thermodynamic Study of Nodal Structure and Multiband Superconductivity of KFe2As2
Shunichiro Kittaka, Yuya Aoki, Naoki Kase +12
The temperature, field, and field-orientation dependences of the electronic specific heat Ce of the ironpnictide superconductor KFe2As2 have been investigated. Thermodynamic eviden…
Edge Current due to Majorana Fermions in Superfluid He A- and B-Phases
Yasumasa Tsutsumi, Kazushige Machida
We propose a method utilizing edge current to observe Majorana fermions in the surface Andreev bound state for the superfluid He A- and B-phases. The proposal is based on self-…
Field dependence of the vortex structure in d-wave and s-wave superconductors
Masanori Ichioka, Akiko Hasegawa, Kazushige Machida
We study the vortex structure and its field dependence within the framework of the quasi-classical Eilenberger theory to find the difference between the d_{x^2-y^2}- and s-wave pai…
Axisymmetric Vortices in Spinor Bose-Einstein Condensates under Rotation
Tomoya Isoshima, Kazushige Machida
The relative stability of various axisymmetric vortices in a spinor Bose-Einstein condensate with F=1 is examined within extended Bogoliubov theory. This yields the phase diagram i…
Field Evolution of the Fulde-Ferrell-Larkin-Ovchinnikov State in a Superconductor with Strong Pauli Effects
Kenta M. Suzuki, Yasumasa Tsutsumi, Noriyuki Nakai +2
The Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) phase in the vortex lattice state is quantitatively studied using the selfconsistent Eilenberger theory in three-dimensional (3D) space.…
Theory of spin-polarized superconductors -- an analogue of superfluid He A-phase
Kazushige Machida
It is shown theoretically that ferromagnetic superconductors, UGe, URhGe, and UCoGe can be described in terms of the A-phase like triplet pairing similar to superfluid He i…
Edge mass current and roles of Majorana Fermions in superfluid 3He A-phase
Yasumasa Tsutsumi, Kazushige Machida
The total angular momentum associated with the edge mass current flowing at the boundary in the superfluid He A-phase confined in a disk is proved to be , consistin…
Double Phase Transitions in Magnetized Spinor Bose-Einstein Condensation
Tomoya Isoshima, Tetsuo Ohmi, Kazushige Machida
It is investigated theoretically that magnetized Bose-Einstein condensation (BEC) with the internal (spin) degrees of freedom exhibits a rich variety of phase transitions, dependin…
Field dependence of the vortex structure in chiral p-wave superconductors
Masanori Ichioka, Kazushige Machida
To investigate the different vortex structure between two chiral pairing p_x +(-) i p_y, we calculate the pair potential, the internal field, the local density of states, and free…
Site-selective nuclear magnetic relaxation time in a superconducting vortex state
Mitsuaki Takigawa, Masanori Ichioka, Kazushige Machida
The temperature and field dependences of the site-selective nuclear spin relaxation time T_1 around vortices are studied comparatively both for s-wave and d-wave superconductors, b…
Modulation vector of the Fulde-Ferrell-Larkin-Ovchinnikov state in CeCoIn5 revealed by high-resolution magnetostriction measurements
Shunichiro Kittaka, Yohei Kono, Kaito Tsunashima +6
The Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state is an exotic superconducting phase formed by Cooper pairs with finite center-of-mass momentum . On theoretical grounds, the sup…
Verification of Anisotropic s-Wave Superconducting Gap Structure in CeRu2 from Low-Temperature Field-Angle-Resolved Specific Heat Measurements
Shunichiro Kittaka, Toshiro Sakakibara, Masato Hedo +2
The field-angle-resolved specific heat C(T,H,phi) of the f-electron superconductor CeRu2 (Tc=6.3 K) has been measured at low temperatures down to 90 mK on two single crystals of sl…
Surface and vortex structures in noncentrosymmetric superconductors under applied magnetic fields
Masatosi Oka, Masanori Ichioka, Kazushige Machida
We investigate how the macroscopic spatial structure of broken inversion symmetry manifests in noncentrosymmetric superconductors, by the microscopic broken inversion symmetry of t…
Theoretical studies on off-axis phase diagrams and Knight shifts in UTe -- Tetra-critical point, d-vector rotation, and multiple phases
Kazushige Machida
Inspired by recent remarkable sets of experiments on UTe: discoveries of the fourth horizontal internal transition line running toward a tetra-critical point (TCP) at =15T,…
Bose-Einstein condensation with internal degrees of freedom in alkali atom gases
Tetsuo Ohmi, Kazushige Machida
The Bogoliubov theory is extended to a Bose-Einstein condensation with internal degrees of freedom, realized recently in Na gases where several hyperfine states are simultan…
Hidden Crossover Phenomena in Strongly Pauli Limited Multiband Superconductors ---Application to CeCuSi
Yasumasa Tsutsumi, Kazushige Machida, Masanori Ichioka
Motivated by recent experiments on heavy fermion materials CeCuSi and UBe, we develop a framework to capture generic properties of multiband superconductors with str…
Textures of Spin-Orbit Coupled F=2 Spinor Bose Einstein Condensates
Takuto Kawakami, Takeshi Mizushima, Kazushige Machida
We study the textures of F=2 spinor Bose-Einstein condensates (BECs) with spin-orbit coupling (SOC) induced by a synthetic non-Abelian gauge field. On the basis of the analysis of…
Violation of the orbital depairing limit in a non-unitary state --on the high field phase in the heavy Fermion superconductor UTe--
Kazushige Machida
A theoretical study is reported on the origin of extremely high upper critical field 70T observed in UTe with the transition temperature T=1.6K-2K, far exceedin…
Multiband superconductivity with unexpected deficiency of nodal quasiparticles in CeCu2Si2
Shunichiro Kittaka, Yuya Aoki, Yasuyuki Shimura +6
Superconductivity in the heavy-fermion compound CeCu2Si2 is a prototypical example of Cooper pairs formed by strongly correlated electrons. For more than 30 years, it has been beli…
Searching for gap zeros in Sr2RuO4 via field-angle-dependent specific-heat measurement
Shunichiro Kittaka, Shota Nakamura, Toshiro Sakakibara +9
The gap structure of SrRuO, which is a longstanding candidate for a chiral p-wave superconductor, has been investigated from the perspective of the dependence of its specif…
Half-Quantum Vortices in Thin Film of Superfluid He
Kenji Kondo, Tetsuo Ohmi, Mikio Nakahara +3
Stability of a half-quantum vortex (HQV) in superfluid He has been discussed recently by Kawakami, Tsutsumi and Machida in Phys. Rev. B {\bf 79}, 092506 (2009). We further exte…