Fukuyama, Hidetoshi, Fuseya, Yuki, Kobayashi, Akito
Features of electronic currents in solids are truly diverse depending on circumstances, e.g. non-equilibrium transport currents leading to dissipation and persistent currents flowing in equilibrium....
Kobayashi, Akito, Suzumura, Yoshikazu, Fukuyama, Hidetoshi, Goerbig, Mark O.
The possible quantum Hall ferromagnet at a filling factor $\nu =0$ is investigated for the zero-energy (N=0) Landau level of the two dimensional massless Dirac fermions in...
Interband Effects of Magnetic Field on Hall Effects for Dirac Electrons in Bismuth (2008)
Fuseya, Yuki, Ogata, Masao, Fukuyama, Hidetoshi
Hall effects are investigated for three-dimensional Dirac electrons as a model of bismuth alloys. It is found that there is unconventional contributions to the Hall conductivity $\sigma_{xy}$...
Single-Component Molecular Metals as Multiband \pi-d Systems (2008)
Seo, Hitoshi, Ishibashi, Shoji, Okano, Yoshinori, Kobayashi, Hayao, Kobayashi, Akiko, Fukuyama, Hidetoshi, ...
Electronic states of single-component molecular metals M(tmdt)2 (M = Ni, Au) are studied theoretically. We construct an effective three-band Hubbard model for each material by numerical fitting to...
Tatara, Gen, Takayama, Toshihiko, Kohno, Hiroshi, Shibata, Junya, Nakatani, Yoshinobu, Fukuyama, Hidetoshi
Threshold current of domain wall motion under spin-polarized electric current in ferromagnets is theoretically studied based on the equation of motion of a wall in terms of collective coordinates....
Hotta, Chisa, Ogata, Masao, Fukuyama, Hidetoshi
We study numerically the ground state properties of the one-dimensional quarter-filled strongly correlated electronic system interacting antiferromagnetically with localized $S=1/2$ spins. It is...
Incommensurate Mott Insulator in One-Dimensional Electron Systems close to Quarter Filling (2005)
Yoshioka, Hideo, Seo, Hitoshi, Fukuyama, Hidetoshi
A possibility of a metal-insulator transition in molecular conductors has been studied for systems composed of donor molecules and fully ionized anions with an incommensurate ratio close to 2:1 based...
New aspects of Verway transition in magnetite (2001)
Seo, Hitoshi, Ogata, Masao, Fukuyama, Hidetoshi
A new mechanism of the Verway transition in magnetite (Fe3O4), which has been argued to be a charge ordering transition so far, is proposed. Based on the mean field calculations for the three band...
Impurity Effects on Quantum Depinning of Commensurate Charge Density Waves (2000)
Yumoto, Masanori, Fukuyama, Hidetoshi, Matsukawa, Hiroshi, Nagaosa, Naoto
We investigate quantum depinning of the one-dimensional (1D) commensurate charge-density wave (CDW) in the presence of one impurity theoretically. Quantum tunneling rate below but close to the...
Interplay between Structure and Electronic Properties in Organic Conductors (1999)
Fukuyama, Hidetoshi, Seo, Hitoshi, Kino, Hiori
It is known that the ground states of organic conductors have a diversity reflecting the spatial arrangement of the constituent molecules within the unit cell. A systematic theoretical search for the...
Low-Temperature Dephasing in Disordered Conductors: the Effect of ``1/f'' Fluctuations (1999)
Imry, Yoseph, Fukuyama, Hidetoshi, Schwab, Peter
Electronic quantum effects in disordered conductors are controlled by the dephasing rate of conduction electrons. This rate is expected to vanish with the temperature. We consider the very intriguing...
Dephasing Effects by Ferromagnetic Boundary on Resistivity in Disordered Metallic Layer (1999)
Tatara, Gen, Fukuyama, Hidetoshi
The resistivity of disordered metallic layer sandwiched by two ferromagnetic layers at low-temperature is investigated theoretically. It is shown that the magnetic field acting at the interface does...
Effects of Disorder on the Competition between Antiferromagnetism and Superconductivity (1999)
Kohno, Hiroshi, Fukuyama, Hidetoshi, Sigrist, Manfred
Motivated by the observation of unusual magnetism in Ce_xCu_2Si_2 ($x\sim 1$), we study the effect of disorder, such as Ce vacancy, on the competition between superconductivity (SC) and...
Strongly Correlated Electrons and Neutron Scattering (1998)
Various aspects of close and interesting relationship between antiferromagnetism and singlet ground states are introduced for which neutron scattering have been playing vital roles. The special...
Yamase, Hiroyuki, Kohno, Hiroshi, Fukuyama, Hidetoshi, Ogata, Masao
In the vicinity of hole density, 1/8, La-based high-$T_{c}$ superconductors exhibit long-range order of incommensurate antiferromagnetism (IC-AF). Motivated by this observation, we explore the...
On the Spin Gap Phase in lambda-(BETS)_2GaX_zY_{4-z} (1998)
Seo, Hitoshi, Fukuyama, Hidetoshi
The nature of the insulating ground state in quasi-two-dimensional organic conductor lambda-(BETS)_2GaX_zY_{4-z}, where the existence of a spin gap is suggested by susceptibility measurement, has...
Charge Ordering and Spin gap in NaV_2O_5 (1998)
Seo, Hitoshi, Fukuyama, Hidetoshi
A possible ground state of NaV_2O_5 is proposed based on the Hartree approximation for both on-site and intersite Coulomb interactions. The results indicate that the intersite Coulomb interaction...
Frustrated Spin System in theta-(BEDT-TTF)_2RbZn(SCN)_4 (1998)
Seo, Hitoshi, Fukuyama, Hidetoshi
The origin of the spin gap behavior in the low-temperature dimerized phase of theta-(BEDT-TTF)_2RbZn(SCN)_4 has been theoretically studied based on the Hartree-Fock approximation for the on-site...
Effect of Local Inhomogeneity on Nucleation; Case of Charge Density Wave Depinning (1998)
Yumoto, Masanori, Fukuyama, Hidetoshi, Matsukawa, Hiroshi
The spatial inhomogeneities are expected to affect nucleation process in an essential way. These effects are studied theoretically by considering the case of the depinning of the charge density wave...
Backward Scattering and Coexistent State in Two-Dimensional Electron System (1998)
Murakami, Masakazu, Fukuyama, Hidetoshi
The results of the mean field studies on the effects of the backward scattering with large momentum transfer in a two-dimensional electron system are extended to the case with various types of the...
Weak Field Magnetoresistance in Quasi-One-Dimensional Systems (1997)
Nakamura, Yoshitaka, Fukuyama, Hidetoshi
Theoretical studies are presented on weak localization effects and magnetoresistance in quasi-one-dimensional systems with open Fermi surfaces. Based on the Wigner representation, the...
Effects of the Backward Scattering in Two-Dimensional Electron System (1997)
Murakami, Masakazu, Fukuyama, Hidetoshi
Effects of the backward scattering with large momentum transfer are examined in two-dimensional electron system with a special emphasis on electrons around ($\pi$,0), (0,$\pi$). The phase diagram is...
Quantized Conductance of One-Dimensional Doped Mott Insulator (1997)
Mori, Michiyasu, Ogata, Masao, Fukuyama, Hidetoshi
The possible modification of quantized conductance of one-dimensional doped Mott insulator, where the Umklapp scattering plays an important role, is studied based on the method by Maslov-Stone and...
Effects of Low Energy Excitations in SNS Junction on the Dynamics of Josephson Phase (1997)
Awaka, Kaoru, Fukuyama, Hidetoshi
The effect of low energy excitation on the dynamics of Josephson phase in SNS junction is investigated. From the microscopic Hamiltonian, the effective action for the phase variable is derived. The...
Effects of Umklapp Scattering on Electronic States in One Dimension (1997)
Murakami, Masakazu, Fukuyama, Hidetoshi
The effects of Umklapp scattering on electronic states are studied in one spatial dimension at absolute zero. The model is basically the Hubbard model, where parameters characterizing the normal...
Antiferromagnetic Phases of One-Dimensional Quarter-Filled Organic Conductors (1997)
Seo, Hitoshi, Fukuyama, Hidetoshi
The magnetic structure of antiferromagnetically ordered phases of quasi-one-dimensional organic conductors is studied theoretically at absolute zero based on the mean field approximation to the...
One-Particle Excitation of the Two-Dimensional Hubbard Model (1997)
Yokoyama, Ken, Fukuyama, Hidetoshi
The real part of the self-energy of interacting two-dimensional electrons has been calculated in the t-matrix approximation. It is shown that the forward scattering results in an anomalous term...
Resistivity due to a Domain Wall in Ferromagnetic Metal (1996)
Tatara, Gen, Fukuyama, Hidetoshi
The resistivity due to a domain wall in ferromagnetic metallic wire is calculated based on the linear response theory. The interaction between conduction electrons and the wall is expressed in terms...
Charge Excitations in Doped Mott Insulator in One Dimension (1996)
Mori, Michiyasu, Fukuyama, Hidetoshi
The doped Mott insulator in one dimension has been studied based on the phase Hamiltonian with the Umklapp scattering process, in which the charge degree of freedom is described by the quantum...
g-on Mean Field Theory of the t-J Model (1996)
Basco, Flordivino, Kohno, Hiroshi, Fukuyama, Hidetoshi, Baskaran, Ganapathy
Implication of our recent proposal [J. Phys. Soc. Jpn. 65 (1996) 687] to treat large-amplitude gauge-field fluctuations around the slave-boson mean-field theory for the t-J model has been explored in...
Macroscopic Quantum Tunneling and Dissipation of Domain Wall in Ferromagnetic Metals (1994)
Tatara, Gen, Fukuyama, Hidetoshi
The depinning of a domain wall in ferromagentic metal via macroscopic quantum tunneling is studied based on the Hubbard model. The dynamics of the magnetization verctor is shown to be governed by an...
Quasi-Particles in Two-Dimensional Hubbard Model: Splitting of Spectral Weight (1994)
Fukuyama, Hidetoshi, Ogata, Masao
It is shown that the energy $(\varepsilon)$ and momentum $(k)$ dependences of the electron self-energy function $ \Sigma (k, \varepsilon + i0) \equiv \Sigma^{R}(k, \varepsilon) $ are, $ {\rm Im}...
Theoretical Study of Friction: A Case of One-Dimensional Clean Surfaces (1994)
Matsukawa, Hiroshi, Fukuyama, Hidetoshi
A new method has been proposed to evaluate the frictional force in the stationary state. This method is applied to the 1-dimensional model of clean surfaces. The kinetic frictional force is seen to...
Macroscopic Quantum Tunneling of a Domain Wall in a Ferromagnetic Metal (1994)
Tatara, Gen, Fukuyama, Hidetoshi
The macroscopic quantum tunneling of a planar domain wall in a ferromagnetic metal is studied by use of an instanton method. Based on the Hubbard model, the effective action of the magnetization is...
Macroscopic Quantum Tunneling of a Domain Wall in a Ferromagnetic Metal (1993)
Tatara, Gen, Fukuyama, Hidetoshi
The macroscopic quantum tunneling of a planar domain wall in a ferromagnetic metal is studied based on the Hubbard model. It is found that the ohmic dissipation is present even at zero temperature...