I. THEORY OF STRONGLY CORRELATED ELECTRON SYSTEMS (2008)
Professors Toshihiro Kawakatsu, Yoshio Kuramoto, Riichiro Saito, Komajiro Niizeki, Hiroaki Kusunose, Tatsuya Nakajima, ...
1. Consequences of multipole orders in CeB6 and CexLa1−xB6 A minimal model for multipole orders in CeB6 is proposed and calculated by mean field theory [1, 2]. Both quadrupole and magnetic ordered...
Predominant Magnetic States in Hubbard Model on Anisotropic Triangular Lattices (2007)
Watanabe, Tsutomu, Yokoyama, Hisatoshi, Tanaka, Yukio, Inoue, Jun-ichiro
Using an optimization variational Monte Carlo method, we study the half-filled-band Hubbard model on anisotropic triangular lattices, as a continuation of the preceding study [J. Phys. Soc. Jpn 75,...
Doublon-Holon Binding Effects on Mott Transitions in Two-Dimensional Bose Hubbard Model (2007)
Yokoyama, Hisatoshi, Ogata, Masao
A mechanism of Mott transitions in a Bose Hubbard model on a square lattice is studied, using a variational Monte Carlo method. Besides an onsite correlation factor, we introduce a four-body...
Yokoyama, Hisatoshi, Ogata, Masao, Tanaka, Yukio
Mechanisms of Mott transitions and dx2-y2-wave superconductivity (SC) are studied in the half-filled-band Hubbard model on square lattices with a diagonal hopping term (t'), using an optimization (or...
Watanabe, Tsutomu, Yokoyama, Hisatoshi, Tanaka, Yukio, Inoue, Jun-ichiro
A half-filled-band Hubbard model on an anisotropic triangular lattice (t in two bond directions and t' in the other) is studied using an optimization variational Monte Carlo method, to consider the...
Watanabe, Tsutomu, Miyata, Takafumi, Yokoyama, Hisatoshi, Tanaka, Yukio, Inoue, Jun-ichiro
Applying a variational Monte Carlo method to a two-dimensional t-J model, we study the nonmonotonic d_{x^2-y^2}-wave superconductivity, observed by Raman scattering and ARPES experiments in the...
I. THEORY OF STRONGLY CORRELATED ELECTRON SYSTEMS (2005)
Professors Toshihiro Kawakatsu, Yoshio Kuramoto, Riichiro Saito, Komajiro Niizeki, Hiroaki Kusunose, Tatsuya Nakajima, ...
1. Octupole order in Ce0.7La0.3B6 probed by resonant X-ray scattering The azimuthal angle dependence observed in the resonant X-ray scattering in phase IV of Ce0.7La0.3B6 is analyzed...
Variational Monte Carlo studies of a t-J model on an anisotropic triangular lattice (2004)
Watanabe, Tsutomu, Yokoyama, Hisatoshi, Tanaka, Yukio, Inoue, Jun-ichiro, Ogata, Masao
With the insulating phase of \kappa-(BEDT-TTF)_2X in mind, we study a t-J model on an anisotropic triangular lattice, where the hopping integral is t' in one of the three directions, using a...
Variational Monte Carlo Studies of Pairing Symmetry for the t-J Model on a Triangular Lattice (2004)
Watanabe, Tsutomu, Yokoyama, Hisatoshi, Tanaka, Yukio, Inoue, Jun-ichiro, Ogata, Masao
As a model of a novel superconductor Na_xCoO_2\cdotyH_2O, a single-band t-J model on a triangular lattice is studied, using a variational Monte Carlo method. We calculate the energies of various...
Yokoyama, Hisatoshi, Tanaka, Yukio, Ogata, Masao, Tsuchiura, Hiroki
Superconductivity in the Hubbard model on a square lattice near half filling is studied using an optimization (or correlated) variational Monte Carlo method. Second-order processes of the...
Variational Monte Carlo studies of attractive Hubbard model I (2002)
Normal states of the attractive Hubbard model, especially in two dimension, are studied in the light of a transition from a Fermi liquid to an insulating or gapped state. A series of variational...
I. THEORY OF STRONGLY CORRELATED ELECTRON SYSTEMS (2000)
Komajiro Niizeki, Hiroshi Yasuhara, Associate Professors, Yoshinori Hayakawa, Hiroaki Kusunose, Yasuyuki Kurata, ...
Dynamical spin correlation function SZZ(Q, ω) with small Q is derived exactly for the spin chain with the 1/r 2 interaction in magnetic field [1]. It is found that only two spinons and one...
Watanabe, Shinji, Yokoyama, Hisatoshi
The bulk properties and impurity effect in the one-dimensional S=1/2 Heisenberg model with dimerization and next-nearest-neighbor exchange are studied by the density matrix renormalization group...
Spin Dynamics of the One-Dimensional J-J' Model and Spin-Peierls Transition in CuGeO_3 (1997)
Yokoyama, Hisatoshi, Saiga, Yasuhiro
Spin dynamics as well as static properties of the one-dimensional J-J' model (S=1/2, J>0 and 0\le \alpha=J'/J\le 0.5) are studied by the exact diagonalization and the recursion method of finite...
Phase Diagram and Pairing Symmetry of the Two-Dimensional t-J Model by a Variation Theory (1996)
Yokoyama, Hisatoshi, Ogata, Masao
Two-dimensional t-J model is studied by a variational Monte Carlo method, using Gutzwiller-Jastrow-type wave functions. Various kinds of superconducting pairing symmetries are compared in order to...
One-Dimensional t-J Model from a Variational Viewpoint (1995)
Yokoyama, Hisatoshi, Ogata, Masao
The one-dimensional (1D) $t$-$J$ model is investigated by using a Gutzwiller-Jastrow-type variation method and the exact diagonalization of small systems. Variational expectation values are estimated...
Variational Monte Carlo Studies of t-J-type Models (1995)
Yokoyama, Hisatoshi, Kuramoto, Yoshio, Ogata, Masao
We give a brief review of recent developments by the variational Monte Carlo method, in addition to some new results. We discuss $t$-$J$-type models: the ordinary $t$-$J$ model in one and two...