Spin torque contribution to the a.c. spin Hall conductivity

TL;DR

This paper investigates how a conserved spin-current operator affects the frequency-dependent spin Hall conductivity in a 2D electron gas with spin-orbit interactions, revealing significant changes in optical spectra and dynamic behavior.

Contribution

It introduces a new definition of spin current that includes a spin torque term, significantly altering the understanding of spin Hall effects in such systems.

Findings

Optical spectrum of spin Hall conductivity shows remarkable changes with the new spin current definition.

The spin torque term significantly influences the magnitude and direction of the dynamic spin Hall current.

The spin Hall response depends strongly on electric field frequency and spin-orbit coupling strengths.

Abstract

Using the recently proposed definition of a conserved spin-current operator [J. Shi et al., Phys. Rev. Lett. 96, 076604 (2006)] we explore the frequency dependent spin Hall conductivity for a two-dimensional electron gas with Rashba and Dresselhaus spin-orbit interaction in response to an oscillating electric field. We show that the optical spectrum of the spin Hall conductivity exhibit remarkable changes when the new definition of spin current is applied. Such behavior is mainly due to a significant contribution of the spin torque term which is absent in the conventional form of the spin current. In addition, it is observed that the magnitude and direction of the dynamic spin Hall current strongly depends on the electric field frequency as with the interplay of the spin-orbit coupling strengths.