A Quantum Spin Hall Round Disk as a Spin Rotator and Filter

TL;DR

This paper theoretically investigates a quantum spin Hall disk that can rotate electron spins via magnetic flux and act as a perfect spin filter, demonstrating potential for spintronic device applications.

Contribution

It introduces a novel spin rotation and filtering mechanism in a quantum spin Hall disk based on interference of edge states and Berry phase effects.

Findings

Spin in-plane component can be rotated by magnetic flux.

The disk acts as a spin filter with 100% polarization ratio.

Spin manipulation is achieved through interference of helical edge states.

Abstract

We study theoretically the spin transport of a Quantum Spin Hall round disk. When an electron traverses the disk in virtue of the edge states, its spin's in-plane component can be rotated by a magnetic flux through the disk. The spin rotation occurs due to the interference of two helical edge states with opposite spins, which is regarded as the Aharonov-Bohm effect in the spin space and a manifestation of the Berry phase. Besides, the disk has a spin filter effect on the tunneling current when we apply an appropriate magnetic field and gate voltage on it. The spin polarization ratio can reach 100% when the couplings between the disk and leads are weak.