Spin polarization direction switch based on an asymmetrical quantum wire

TL;DR

This paper proposes a device using an asymmetrical quantum wire with Rashba spin-orbit coupling that can switch the direction of spin polarization by reversing the external current, demonstrating robustness against disorder.

Contribution

It introduces a novel spin polarization switch based on symmetry-breaking in an asymmetrical quantum wire with Rashba SOC, highlighting its robustness and potential for applications.

Findings

Spin polarization direction can be reversed by changing current direction.

The device's spin polarization is robust against disorder.

Symmetry considerations explain the polarization switching mechanism.

Abstract

A scheme for a spin polarization direction switch is investigated by studying the spin-dependent electron transport of an asymmetrical quantum wire (QW) with Rashba spin-orbit coupling (SOC). It is found that the magnitude of the spin-polarized current in the backward biased case is equal to it in the forward biased case but their signs are contrary. This results indicate that the spin polarization direction can be switched by changing the direction of the external current. The physical mechanism of this device may arise from the symmetries in the longitudinal and transverse directions are broken but $C_2$-rotation and time-reversal symmetries are still reserved. Further studies show that the spin polarization is robust against disorder, displaying the feasibility of the proposed structure for a potential application.