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Sakai, Toru; Nakano, Hiroki*
Journal of Physics; Conference Series, 568(4), p.042025_1 - 042025_6, 2014/12
Times Cited Count：0 Percentile：0.05(Physics, Applied)The kagome-lattice antiferromagnets have attracted a lot of interest in the field of the low-temperature physics. It exhibits some exotic field-induced phenomena, like a magnetization plateau, jump etc. Our previous large-scale yumerical exact diagonalization study on the S=1/2 kagome-lattice antiferromagnet revealed that a novel field-induced phenomenon, "the magnetization ramp", occurs at 1/3 of the saturation magnetization. It is characterized by different critical exponents between the lower-field and higher-field sides of the magnetization curve. In order to clarify unconventional properties around the 1/3 magnetization, we considered some extended lattice models; a distorted kagome lattice and distorted triangular lattice etc. Our numerical exact diagonalization study also indicates that the ground state of the kagome-lattice antiferromagnet is gapless quantum spin liquid.
Nagai, Yuki; Ota, Yukihiro; Machida, Masahiko
Journal of Physics; Conference Series, 568(2), p.022030_1 - 022030_5, 2014/12
Times Cited Count：0 Percentile：0.05(Physics, Applied)We study the robustness against non-magnetic impurities in a three-dimensional topological superconductor, focusing on an effective model (massive Dirac Bogoliubov-de Gennes (BdG) Hamiltonian with 
-wave on-site pairing) of Cu
Bi
Se
with the parameter set determined by the first-principles calculation. With the use of the self-consistent 
-matrix approximation for impurity scattering, we discuss the impurity-concentration dependence of the zero-energy density of states. We show that a single material variable, measuring relativistic effects in the Dirac-BdG Hamiltonian, well characterizes the numerical results. In the nonrelativistic limit, the odd-parity fully-gapped topological superconductivity is fragile against non-magnetic impurities, since this superconductivity can be mapped onto the 
-wave superconductivity. On the other hand, in the ultrarelativistic limit, the superconductivity is robust against the non-magnetic impurities, since the effective model has the -wave superconductivity. We derive the effective Hamiltonian in the both limit.
Higashi, Yoichi*; Nagai, Yuki; Yoshida, Tomohiro*; Yanase, Yoichi*
Journal of Physics; Conference Series, 568(2), p.022018_1 - 022018_5, 2014/12
Times Cited Count：4 Percentile：82.5(Physics, Applied)We numerically study the electronic structure of a single vortex in two dimensional superconducting bilayer systems within the range of the mean-field theory. The lack of local inversion symmetry in the system is taken into account through the layer dependent Rashba spin-orbit coupling. The spatial profiles of the pair potential and the local quasiparticle density of states are calculated in the clean spin-singlet superconductor on the basis of the quasiclassical theory. In particular, we discuss the characteristic core structure in the pair-density wave state, which is spatially modulated exotic superconducting phase in a high magnetic field.
Kawakami, Takuto*; Nagai, Yuki; Yoshizawa, Shunsuke*; Kim, H.*; Hasegawa, Yukio*; Nakayama, Tomonobu*; Uchihashi, Takashi*; Hu, X.*
Journal of Physics; Conference Series, 568(2), p.022022_1 - 022022_5, 2014/12
Times Cited Count：2 Percentile：67.35(Physics, Applied)no abstracts in English
LaTiOOkuda, Tetsuji*; Hata, Hiroto*; Eto, Takahiro*; Nishina, Kosuke*; Kuwahara, Hideki*; Nakamura, Mitsutaka; Kajimoto, Ryoichi
Journal of Physics; Conference Series, 568(Part 2), p.022035_1 - 022035_5, 2014/12
Times Cited Count：7 Percentile：91.32(Physics, Applied)Sakai, Toru; Nakano, Hiroki*; Okunishi, Koichi*
Journal of Physics; Conference Series, 568(4), p.042024_1 - 042024_5, 2014/00
Times Cited Count：3 Percentile：76.6(Physics, Applied)The spin nanotube is investigated by the numerical diagonalization and the level spectroscopy analysis. As a result, the quantum phase transition between the spin gap and gapless phases was revealed to occur with respect to the ratio of the rung and leg exchange interactions.
Kajimoto, Ryoichi; Fujita, Masaki*; Nakajima, Kenji; Iida, Kazuki*
no journal, ,
