S. Maekawa

Electronic structure and effective Hamiltonian in perovskite Mn oxides

Abstract In order to investigate electronic and magnetic structures in perovskite Mn oxides, we consider the effective Hamiltonian derived from the generalized ferromagnetic Kondo-Hubbard model. The mean-field approximation is adopted to analyze the ordered states of the spin and orbital degrees of freedom in the insulating state. As the excitations in the ordered states, we consider the spin and orbital waves and their dispersion relations are calculated.

Bogoliubov quasiparticle excitations in the two-dimensional t-J model.

Using a proposed numerical technique for calculating anomalous Greens functions characteristic of superconductivity, we show that the low-lying excitations in a wide parameter and doping region of the two-dimensional t-J model are well described by the picture of dressed Bogoliubov quasiparticles in the BCS pairing theory. The pairing occurs predominantly in the

One-particle excitation spectra, optical conductivity and O ls x-ray absorption spectra in high-Tc cuprates: a cluster model approach

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ANOMALOUS SPIN AND CHARGE DYNAMICS OF THE T-J MODEL AT LOW DOPING

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Theory of spin‐dependent tunneling and transport in magnetic nanostructures (invited)

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Gutzwiller wave function in the three-band Hubbard model: A variational Monte Carlo study.

-wave channel and the energy gap has a size

Spin dependent resistivity in magnetic alloys and multilayers

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Density of states of a hole in the half-filled Hubbard model

\ensuremath{\simeq}0.15J\char21{}0.27J between quarter and half fillings. Opening of the superconducting gap in the photoemission and inverse-photoemission spectra is demonstrated.

Electronic Properties in the Cu-Oxide Superconductors

Abstract A systematic study of the one-particle excitation spectra, the optical conductivity (σ(ω)) and the O ls X-ray absorption spectra (XAS) in high-Tc cuprates is given by means of the exact diagonalization of finite-size clusters. The dramatic change of σ(ω) and O ls XAS upon carrier-doping is related to the features of the one-particle excitation spectra such as the shift of the Fermi level and the reconstruction of the spectral weights. The quantitative analyses of the material dependence of, in particular, O ls XAS clarify the nature of the carrier (both electron and hole)-doped states.

Impurity effect in the 2D t-J model

We present an exact diagonalization study of the dynamical spin and density correlation function of the 2D t-J model for hole doping < 25%. Both correlation functions show a remarkably regular, but completely different scaling behaviour with both hole concentration and parameter values: the density correlation function is consistent with that of bosons corresponding to the doped holes and condensed into the lowest state of the noninteracting band of width 8t, the spin correlation function is consistent with Fermions in a band of width J. We show that the spin bag picture gives a natural explanation for this unusual behaviour.