Magnus spin Hall and spin Nernst effects in gapped 2D Rashba systems

TL;DR

This paper investigates the Magnus spin and charge transport phenomena in gapped 2D Rashba systems, revealing how the gap and Fermi surface topology influence the Magnus Hall and Nernst effects, with specific focus on spin polarization and conductivity behaviors.

Contribution

It introduces the concept of Magnus spin transport in gapped 2D Rashba systems and analyzes its dependence on the gap and Fermi surface topology, providing new insights into spin and charge Hall effects.

Findings

Magnus spin Hall conductivity vanishes as the gap approaches zero.

Magnus spin currents with perpendicular spin polarization are finite.

Conductivities show plateaus and peaks at the gap edges.

Abstract

We study the Magnus transport in a gapped 2D electron gas with Rashba spin-orbit coupling using semiclassical Boltzmann transport formalism. Apart from its signature in the charge transport coefficients, the inclusion of Magnus velocity in the spin current operator enables us to study Magnus spin transport in the system. In particular, we study the roles of mass gap and Fermi surface topology on the behavior of Magnus Hall and Nernst conductivities and their spin counterparts. We find that the Magnus spin Hall conductivity vanishes in the limit of zero gap, unlike the universal spin Hall conductivity $\sigma_s=e/(8\pi)$. The Magnus spin currents with spin polarization perpendicular to the applied bias (electrical/thermal) are finite while with polarization along the bias vanishes. Each Magnus conductivity displays a plateau as Fermi energy sweeps through the gap and has peaks (whose magnitudes decrease with the gap) when the Fermi energy is at the gap edges.