Topological states in a transition metal oxide Na2IrO3 (2008)
Shitade, Atsuo, Katsura, Hosho, Qi, Xiao-Liang, Zhang, Shou-Cheng, Nagaosa, Naoto
The electronic state of an Ir oxide, Na$_2$IrO$_3$ with the honeycomb structure is analyzed theoretically as a representative system where both the spin-orbit interaction and the electron correlation...
Current-induced dynamics of spiral magnet (2008)
Goto, Kohei, Katsura, Hosho, Nagaosa, Naoto
We study the dynamics of the spiral magnet under the charge current by solving the Landau-Lifshitz-Gilbert equation numerically. In the steady state, the current ${\vec j}$ induces (i) the parallel...
Block Spin Density Matrix of the Inhomogeneous AKLT Model (2008)
Xu, Ying, Katsura, Hosho, Hirano, Takaaki, Korepin, Vladimir E.
We study the inhomogeneous generalization of a 1-dimensional AKLT spin chain model. Spins at each lattice site could be different. Under certain conditions, the ground state of this AKLT model is...
Quantum Dynamics of Multiferroic Helimagnets: a Schwinger-Boson Approach (2008)
Katsura, Hosho, Onoda, Shigeki, Han, Jung Hoon, Nagaosa, Naoto
We study the quantum dynamics/fluctuation of the cycloidal helical magnet in terms of the Schwinger boson approach. In sharp contrast to the classical fluctuation, the quantum fluctuation is...
Degeneracy and Consistency Condition of Berry phases: Gap Closing under the Twist (2008)
Hirano, Takaaki, Katsura, Hosho, Hatsugai, Yasuhiro
We have discussed a consistency condition of Berry phases defined by a local gauge twist and spatial symmetries of the many body system. It imposes a non trivial gap closing condition under the gauge...
Entanglement and Density Matrix of a Block of Spins in AKLT Model (2008)
Xu, Ying, Katsura, Hosho, Hirano, Takaaki, Korepin, Vladimir E.
We study a 1-dimensional AKLT spin chain, consisting of spins $S$ in the bulk and $S/2$ at both ends. The unique ground state of this AKLT model is described by the Valence-Bond-Solid (VBS) state. We...
Entanglement in an SU(n) Valence-Bond-Solid State (2007)
Katsura, Hosho, Hirano, Takaaki, Korepin, Vladimir E.
We investigate entanglement properties in the ground state of the open/periodic SU($n$) generalized valence-bond-solid state consisting of representations of SU($n$). We obtain exact expression for...
Hirano, Takaaki, Katsura, Hosho, Hatsugai, Yasuhiro
We characterize several phases of gapped spin systems by local order parameters defined by quantized Berry phases. This characterization is topologically stable against any small perturbation as long...
Entanglement Entropy in the Calogero-Sutherland Model (2007)
Katsura, Hosho, Hatsuda, Yasuyuki
We investigate the entanglement entropy between two subsets of particles in the ground state of the Calogero-Sutherland model. By using the duality relations of the Jack symmetric polynomials, we...
Exact Analysis of Entanglement in Gapped Quantum Spin Chains (2007)
Katsura, Hosho, Hirano, Takaaki, Hatsugai, Yasuhiro
We investigate the entanglement properties of the valence-bond-solid states with generic integer-spin $S$. Using the Schwinger boson representation of the valence-bond-solid states, the entanglement...
Nonequilibrium Kondo problem with spin-dependent chemical potentials: Exact results (2007)
We give a brief review of the Kondo effect and exactly solve the nonequilibrium Kondo problem at the special point in the parameter space of the model with spin-dependent chemical potentials. Using...
Quantum cloning with nonlocal assistance: Complement of Jozsa's stronger no-cloning theorem (2006)
Azuma, Koji, Koashi, Masato, Katsura, Hosho, Imoto, Nobuyuki
We investigate the cases where a set $S$ of states $\{\ket{\psi_i} \}$ cannot be cloned by itself, but is clonable with the help of another system prepared in state $\hat{\rho}_i$. When $S$ is...
Electron localization/delocalization in incommensurate helical magnets (2006)
Tanaka, Shu, Katsura, Hosho, Nagaosa, Naoto
The electronic states in incommensurate (IC) helical magnets are studied theoretically from the viewpoint of the localization/delocalization. It is found that in the multi-band system with...
Dynamical magneto-electric coupling in helical magnets (2006)
Katsura, Hosho, Balatsky, Alexander V., Nagaosa, Naoto
Collective mode dynamics of the helical magnets coupled to electric polarization via spin-orbit interaction is studied theoretically. The soft modes associated with the ferroelectricity are not the...
Katsura, Hosho, Balatsky, Alexander V., Nussinov, Zohar, Nagaosa, Naoto
We present a theory of Landau-Lifshitz-Gilbert damping $\alpha$ for a localized spin ${\vec S}$ in the junction coupled to the conduction electrons in both leads under an applied volatege $V$. We...
Spin current and magneto-electric effect in non-collinear magnets (2004)
Katsura, Hosho, Nagaosa, Naoto, Balatsky, Alexander V.
A new microscopic mechanism of the magneto-electric (ME) effect based on the spin supercurrent is theoretically presented for non-collinear magnets. The close analogy between the superconductors...
A Dirac particle in general dimensions moving in a 1/r potential is shown to have an exact N = 2 supersymmetry, for which the two supercharge operators are obtained in terms of (a D-dimensional...