Spin polarization of electrons with Rashba double-refraction

TL;DR

This paper shows how Rashba spin-orbit coupling in semiconductor heterostructures can generate and control spin-polarized currents without ferromagnetic leads, using spin-double refraction and incidence angle dependence.

Contribution

It introduces a novel method to produce and modulate spin-polarized currents via spin-double refraction, enabling a spin-field-effect transistor without ferromagnetic components.

Findings

Transmission halves beyond a critical incidence angle.

Significant spin-polarization appears at certain angles.

Modulation of current intensity and polarization with spin-orbit strength.

Abstract

We demonstrate how the Rashba spin-orbit coupling in semiconductor heterostructures can produce and control a spin-polarized current without ferromagnetic leads. Key idea is to use spin-double refraction of an electronic beam with a nonzero incidence angle. A region where the spin-orbit coupling is present separates the source and the drain without spin-orbit coupling. We show how the transmission and the beam spin-polarization critically depend on the incidence angle. The transmission halves when the incidence angle is greater than a limit angle and a significant spin-polarization appears. Increasing the spin-orbit coupling one can obtain the modulation of the intensity and of the spin-polarization of the output electronic current when the input current is unpolarized. Our analysis shows the possibility to realize a spin-field-effect transistor based on the propagation of only one mode with the region with spin-orbit coupling. Where the original Datta and Das device [Appl.Phys.Lett. {\bf 56}, 665 (1990)] use the spin-precession that originates from the interference between two modes with orthogonal spin.