Spin polarization of electron current through a potential barrier in two-dimensional structures with spin-orbit interaction

TL;DR

This paper demonstrates that in two-dimensional systems with spin-orbit interaction, an unpolarized electron current can acquire significant spin polarization after passing through a potential barrier, with the effect depending on the Fermi energy and distance from the barrier.

Contribution

It reveals the mechanism of spin polarization generation in 2D systems with SOI and proposes a method to transfer spin-polarized current into regions without SOI with minimal loss.

Findings

Spin polarization occurs after passing through the barrier.

Maximum polarization (>50%) near the barrier's potential maximum.

Spin current oscillates and reaches a steady value with distance.

Abstract

We show that an initially unpolarized electron flow acquires spin polarization after passing through a lateral barrier in two-dimensional (2D) system with spin-orbit interaction (SOI) even if the current is directed normally to the barrier. The generated spin current depends on the distance from the barrier. It oscillates with the distance in the vicinity of the barrier and asymptotically reaches a constant value. The most efficient generation of the spin current (with polarization above 50%) occurs, when the Fermi energy is near the potential barrier maximum. Since the spin current in SOI medium is not unambiguously defined we propose to pass this current from the SOI region into a contacting region without SOI and show, that the spin polarization loss under such transmission can be negligible.