Theory of Spin-Charge Coupled Transport in a Two-Dimensional Electron Gas with Rashba Spin-Orbit Interactions

TL;DR

This paper develops a comprehensive microscopic linear response framework to describe coupled spin and charge transport in a 2DEG with Rashba spin-orbit interaction, capturing various spin-related effects and applicable to experimental modeling.

Contribution

It introduces a set of general equations for spin-charge coupled transport in 2DEGs with Rashba SO interaction, linking microscopic theory to experimental observables.

Findings

Voltage develops between ferromagnetic contacts during spin injection, depending on magnetization orientation.

The equations account for spin accumulation, diffusion, and relaxation effects.

Application to a simple electrical spin injection experiment demonstrates practical relevance.

Abstract

We use microscopic linear response theory to derive a set of equations that provide a complete description of coupled spin and charge diffusive transport in a two-dimensional electron gas (2DEG) with the Rashba spin-orbit (SO) interaction. These equations capture a number of interrelated effects including spin accumulation and diffusion, Dyakonov-Perel spin relaxation, magnetoelectric, and spin-galvanic effects. They can be used under very general circumstances to model transport experiments in 2DEG systems that involve either electrical or optical spin injection. We comment on the relationship between these equations and the exact spin and charge density operator equations of motion. As an example of the application of our equations, we consider a simple electrical spin injection experiment and show that a voltage will develop between two ferromagnetic contacts if a spin-polarized current is injected into a 2DEG, that depends on the relative magnetization orientation of the contacts. This voltage is present even when the separation between the contacts is larger than the spin diffusion length.