Related papers: Derivation of effective spin models from a three b…
We preform a multi-orbital analysis on the novel superconductivity in Na_{x}CoO_{2} \cdot yH_{2}O. We construct a three-orbital model which reproduces the band structure expected from the LDA calculation. The effective interaction leading…
To leading order in displacement size, the scattering of electrons in a Cu-O plane from O displacements perpendicular to that plane is due to spin-orbit coupling. This scattering is investigated with the following results: (1) As a…
Using a numerically exact technique we study spin transport and the evolution of spin-density excitation profiles in a disordered spin-chain with long-range interactions, decaying as a power-law, $r^{-\alpha}$ with distance and $\alpha<2$.…
The spin-lattice relaxation rate $1/T_1$ and the spin echo decay rate $1/T_{2G}$ for the 2D Heisenberg model are calculated using quantum Monte Carlo and maximum entropy analytic continuation. The results are compared to recent experiments…
In this paper, from the microscopic Hubbard Hamiltonian we extract the local spin-singlet amplitude due to short-range spin correlations, and quantify its strength near half-filling. As a first application of the present approach, we study…
We study the spin-orbit coupling in spin-triplet Cooper pairs and clarify multiple superconducting (SC) phases in Sr$_2$RuO$_4$. Based on the analysis of the three-orbital Hubbard model with atomic LS coupling, we show some selection rules…
We calculate the effective interaction $W_{eff}$ between two holes added to the ground state of the repulsive three-band Hubbard model. To make contact with Cooper theory and with earlier Hubbard model cluster studies, we first use a…
We apply density functional theory band structure calculations, the coupled-cluster method, and exact diagonalization to investigate the microscopic magnetic model of the spin-1/2 compound Cu2GeO4. The model is quasi-two-dimensional, with…
We discuss a microscopic mechanism of the spin-tiplet superconductivity in the quasi-two-dimensional ruthenium oxide Sr2RuO4 on the basis of two-dimensional three-band Hubbard model. We solve the linearized Eliashberg equation by taking…
We study spin dynamics of a spin-Peierls chain with nearest-neighbor and next-nearest-neighbor Heisenberg spin exchange interactions together with a gapped and dispersionless phonon. The dynamical spin correlation function and phonon…
The model developed for LaMnO$_3$ addresses the spin-orbital order by superexchange and Jahn-Teller orbital interactions in the cubic (perovskite) symmetry up to now whereas real crystal structure is strongly deformed. We identify and…
We investigate the Cu $L_3$ edge resonant inelastic x-ray scattering (RIXS) spectra of a quasi-1D antiferromagnet Ca$_2$CuO$_3$. In addition to the magnetic excitations, which are well-described by the two-spinon continuum, we observe two…
A recent density functional theory (DFT) based analysis, complemented with Quantum Monte Carlo calculations revealed a highly spin-frustrating nature of the one-dimensional spin-$\frac{1}{2}$ compound $Cs_2CuAl_4O_8$ that comprises of…
Randomly diluted quantum boson and spin models in two dimensions combine the physics of classical percolation with the well-known dimensionality dependence of ordering in quantum lattice models. This combination is rather subtle for models…
Several puzzling aspects of interplay of the experimental lattice distortion and the the magnetic properties of four narrow $t_{2g}$-band perovskite oxides (YTiO$_3$, LaTiO$_3$, YVO$_3$, and LaVO$_3$) are clarified using results of…
While the enhancement of the spin-space symmetry from the usual $\mathrm{SU}(2)$ to $\mathrm{SU}(N)$ is promising for finding nontrivial quantum spin liquids, its realization in magnetic materials remains challenging. Here we propose a new…
We use the spin-fermion model to describe the CuO$_2$ planes of the high-Tc superconductors. Using a large wavelength approach, we show that the ferromagnetic component of the Cu spin fluctuations couple to the oxygen holes producing a…
Effect of quantum fluctuations concerned with the orbital degrees of freedom is discussed for the model with SU(4) symmetry in one dimension. An effective Hamiltonian is derived from the orbitally degenerate Hubbard model at quarter…
Analyzing the motion of low--spin $(s=1/2)$ holes in a high--spin $(S=1)$ background, we derive a sort of generalized t--J Hamiltonian for the $\rm NiO_2$ planes of Sr--doped nickelates. In addition to the rather complex carrier--spin and…
The electronic structure of the ferromagnetic semiconductor EuO is investigated by means of spin- and angle-resolved photoemission spectroscopy (spin-ARPES) and density functional theory. EuO exhibits unique properties of hosting both…