Enhancement of polarization in a spin-orbit coupling quantum wire with a constriction

TL;DR

This paper demonstrates that introducing a constriction in a spin-orbit coupled quantum wire significantly enhances spin polarization by confining electrons and promoting sub-band mixing and interference effects, improving spin-filtering efficiency.

Contribution

The study reveals that a constriction in a quantum wire with spin-orbit coupling greatly amplifies spin-filtering effects through channel confinement and scattering mechanisms, analyzed via perturbation theory.

Findings

Spin polarization is significantly increased with a constriction.

Confinement to a single channel enhances spin-filtering.

Interference and sub-band mixing are key to the effect.

Abstract

We investigate the enhancement of spin polarization in a quantum wire in the presence of a constriction and a spin-orbit coupling segment. It is shown that the spin-filtering effect is significantly heightened in comparison with the configuration without the constriction. It is understood in the studies that the constriction structure plays a critical role in enhancing the spin filtering by means of confining the incident electrons to occupy one channel only while the outgoing electrons occupy two channels. The enhancement of spin-filtering has also been analyzed within the perturbation theory. Because the spin polarization arises mainly from the scattering between the constriction and the segment with spin-orbit coupling, the sub-band mixing induced by spin-orbit interaction in the scattering process and the interferences result in higher spin-filtering effect.