A drift-diffusion model for spin-polarized transport in a two-dimensional non-degenerateelectron gas controlled by spin–orbit interaction

Abstract

We apply the Wigner function formalism to derive drift-diffusion transport equations forspin-polarized electrons in a III–V semiconductor single quantum well. The electron spindynamics is controlled by the spin–orbit interaction which is linear in the momentum. Inthe transport regime studied, the electron momentum scattering rate is appreciably fasterthan the spin dynamics. A set of transport equations is defined in terms of a particledensity, a spin density, and the respective fluxes. The model developed allows study of thecoherent dynamics of a non-equilibrium spin polarization. As an example, we consider astationary transport regime for a heterostructure grown along the (0, 0, 1) crystallographicdirection. Due to the interplay of the Rashba and Dresselhaus spin–orbit terms, the spindynamics strongly depends on the transport direction. The model is consistentwith the results of pulse–probe measurements of the spin coherence in strainedsemiconductor layers. It can be useful in studying properties of spin-polarizedtransport and modelling spintronic devices operating in the diffusive transport regime.