Deduction of Pure Spin Current from Spin Linear and Circular Photogalvanic Effect in Semiconductor Quantum Wells

TL;DR

This paper demonstrates how to generate and measure pure spin currents in semiconductor quantum wells using spin photogalvanic effects induced by polarized light, providing a new method for studying spin transport.

Contribution

It introduces a novel approach to deduce pure spin currents from measurable spin photocurrents caused by different light polarizations in semiconductor quantum wells.

Findings

Linearly polarized light can inject pure spin currents via Rashba spin-orbit coupling.

Circularly polarized light can induce spin-dependent photocurrents.

A relation between photocurrent and spin current allows experimental deduction of spin currents.

Abstract

We study the spin photogalvanic effect in two-dimensional electron system with structure inversion asymmetry by means of the solution of semiconductor optical Bloch equations. It is shown that a linearly polarized light may inject a pure spin current in spin-splitting conduction bands due to Rashba spin-orbit coupling, while a circularly polarized light may inject spin-dependent photocurrent. We establish an explicit relation between the photocurrent by oblique incidence of a circularly polarized light and the pure spin current by normal incidence of a linearly polarized light such that we can deduce the amplitude of spin current from the measured spin photocurrent experimentally. This method may provide a source of spin current to study spin transport in semiconductors quantitatively.