Quantum Spin Current Induced Through Optical Fields

TL;DR

This paper proposes a novel optical method to generate pure quantum spin currents in semiconductors without relying on spin-orbit interaction, analyzing impurity effects and demonstrating the robustness of the effect.

Contribution

It introduces a new scheme using optical dipole transitions in a three-level system to produce quantum spin currents without spin-orbit coupling.

Findings

Pure quantum spin current can be generated optically.

Vertex correction of spin Hall conductivity is zero with impurities.

The scheme is robust against nonmagnetic impurities.

Abstract

We propose a scheme to generate quantum spin current via optical dipole transition process. By coupling a three-level system based on the spin states of charged particles (electrons or holes in semiconductor) to the angular momentum states of the radiation, we show that a pure quantum spin current can be generated. No spin-orbit interaction is needed in this scheme. We also calculate the effect of nonmagnetic impurities on the created spin currents and show that the vertex correction of the spin hall conductivity in the ladder approximation is exactly zero.