arXiv subjects

Zhigang Wang

Publications and source records attributed to Zhigang Wang.

148 records · Page 9Linked to original sources

arXiv2007

Orbital magnetization and its effect in antiferromagnets on the distorted fcc lattice

We study the intrinsic orbital magnetization (OM) in antiferromagnets on the distorted face-centered-cubic lattice. The combined lattice distortion and spin frustration induce nontrivial $k$-space Chern invariant, which turns to result in profound effects on the OM properties. We derive a specific relation between the OM and the Hall conductivity, according to which it is found that the intrinsic OM vanishes when the electron chemical potential lies in the Mott gap. The distinct behavior of the intrinsic OM in the metallic and insulating regions is shown. The Berry phase effects on the thermoelectric transport is also discussed.

cond-mat.mes-hall↗

arXiv2007

Conserved spin Hall conductance in two dimensional electron gas in a perpendicular magnetic field

Using the microscopic theory of the conserved spin current [Phys. Rev. Lett. \textbf{96}, 076604 (2006)], we investigate the spin Hall effect in the two dimensional electron gas system with a perpendicular magnetic field. The spin Hall conductance $σ_{μν}^{s}$ as a response to the electric field consists of two parts, i.e., the conventional part $σ_{μν}^{s0}$ and the spin torque dipole correction $σ_{μν}^{sτ}$. It is shown that the spin-orbit coupling competes with Zeeman splitting by introducing additional degeneracies between different Landau levels at certain values of magnetic field. These degeneracies, if occurring at the Fermi level, turn to give rise to resonances in both $σ_{μν}^{s0}$ and $σ_{μν}^{sτ}$ in spin Hall conductance. Remarkably, both of these two components have the same sign in the wide range of variation in the magnetic field, which result in an overall enhancement of the total spin Hall current. In particular, the magnitude of $σ_{μν}^{sτ}$ is much larger than that of $σ_{μν}^{s0}$ around the resonance.

cond-mat.mes-hall↗

arXiv2007

Orbital magnetization and its effects in spin-chiral ferromagnetic Kagome lattice

Recently, Berry phase in the semiclassical dynamical of Bloch electrons has been found to make a correction to the phase-space density of states and a general multi-band formula for finite-temperature orbital magnetization has been given [Phys. Rev. Lett. \textbf{97}, 026603 (2006)], where the orbital magnetization $\mathcal{M}$ consists of two parts, i.e., the conventional part $M_{c}$ and the Berry-phase correction part $M_Ω$. Using this general formula, we theoretically investigate the orbital magnetization and its effects on thermoelectric transport and magnetic susceptibility properties of the two-dimensional \textit{kagomé} lattice with spin anisotropies included. The study in this paper is highly interesting by the occurrence of nonzero Chern number in the lattice. The spin chirality parameter $ϕ$ (see text) results in profound effects on the orbital magnetization properties. It is found that the two parts in orbital magnetization opposite each other. In particular, we show that $M_{c}$ and $M_Ω$ yield the paramagnetic and diamagnetic responses, respectively. It is further shown that the orbital magnetization displays fully different behavior in the metallic and insulating regions, which is due to the different roles $M_{c}$ and $M_Ω$ play in these two regions. The anomalous Nernst conductivity is also calculated, which displays a peak-valley structure as a function of the electron Fermi energy.

cond-mat.mes-hall↗

arXiv2007

Theory of conserved spin current and its application to two dimensional hole gas

We present a detailed microscopic theory of the conserved spin current which is introduced by us [Phys. Rev. Lett. \textbf{96}, 196602 (2006)] and satisfies the spin continuity equation even for spin-orbit coupled systems. The spin transport coefficients $σ_{μν}^{s}$ as a response to the electric field are shown to consist of two parts, i.e., the conventional part $σ_{μν}^{s0}$ and the spin torque dipole correction $σ_{μν}^{sτ}$. As one key result, an Onsager relation between $σ_{μν}^{s}$ and other kinds of transport coefficients are shown. The expression for $σ_{μν}^{s}$ in terms of single-particle Bloch states are derived, by use of which we study the conserved spin Hall conductivity in the two dimensional hole gas modeled by a combined Luttinger and SIA Rashba spin-orbit coupling. It is shown that the two components in spin Hall conductivity usually have the opposite contributions. While in the absence of Rashba spin splitting, the spin Hall transport is dominated by the conventional contribution, the presence of Rashba spin splitting stirs up a large enhancement of the spin torque dipole correction, leading to an overall sign change for the total spin Hall conductivity. Furthermore, an approximate two-band calculation and the subsequent comparison with the exact four-band results are given, which reveals that the coupling between the heavy hole and light hole bands should be taken into account for strong Rashba spin splitting.

cond-mat.mes-hall↗