Photon-assisted spin transport in a two-dimensional electron gas

Abstract

We study spin-dependent transport in a two-dimensional electron gas subjected to an external steplike potential $V(x)$ and irradiated by an electromagnetic field (EF). In the absence of EF, the electronic spectrum splits into spin subbands originating from the ``Rashba'' spin-orbit coupling. We show that the resonant interaction of propagating electrons with the component EF parallel to the barrier induces a nonequilibrium dynamic gap $(2{\ensuremath{\Delta}}_{R})$ between the spin subbands. Existence of this gap results in coherent spin-flip processes that lead to a spin-polarized current and a large magnetoresistance, i.e., the spin-valve effect. These effects may be used for controlling spin transport in semiconducting nanostructures, e.g., spin transistors, spin-blockade devices, etc., by variation of the intensity $S$ and frequency $\ensuremath{\omega}$ of the external radiation.