Spin Filtering in a Nonuniform Quantum Wire with Rashba Spin-Orbit Interaction

TL;DR

This paper theoretically demonstrates how a nonuniform quantum wire with Rashba spin-orbit interaction can generate large, tunable spin-polarized currents through Fano resonances, offering a magnetic-material-free spin filter design.

Contribution

It introduces a method to generate and control large spin-polarized currents in a nonuniform quantum wire using Rashba SOI and Fano resonances, without magnetic materials.

Findings

Large spin-polarized current can be generated at Fano resonances.

Spin polarization magnitude is tunable via Rashba SOI and structural parameters.

Effective spin filtering achieved even with strong disorder.

Abstract

We investigate theoretically the spin-polarized electron transport for a wide-narrow-wide (WNW) quantum wire under the modulation of Rashba spin-orbit interaction (SOI). The influence of both the structure of the quantum wire and the interference between different pairs of subbands on the spin-polarized electron transport is taken into account simultaneously via the spin-resolved lattice Green function method. It is found that a very large vertical spin-polarized current can be generated by the SOI-induced effective magnetic field at the structure-induced Fano resonance even in the presence of strong disorder. Furthermore, the magnitude of the spin polarization can be tuned by both the Rashba SOI strength and structural parameters. Our results may provide an effective way to design a spin filter device without containing any magnetic materials or applying a magnetic field.