Electrical manipulation and measurement of spin properties of quantum spin Hall edge states

TL;DR

This paper explores how gate-controlled Rashba spin-orbit coupling can electrically manipulate and measure the spin properties of quantum spin Hall edge states in HgTe quantum wells, revealing conductance changes linked to spin orientation.

Contribution

It introduces a novel experimental setup for probing spin helicity electrically without magnetic materials or fields, advancing control over quantum spin Hall edge states.

Findings

Rashba coupling can tune the spin orientation of edge states.

Tilted spin orientation reduces two-terminal conductance.

Conductance behavior aligns with Luttinger liquid models.

Abstract

We study effects of a gate-controlled Rashba spin-orbit coupling to quantum spin-Hall edge states in HgTe quantum wells. A uniform Rashba coupling can be employed in tuning the spin orientation of the edge states while preserving the time-reversal symmetry. We introduce a sample geometry where the Rashba coupling can be used in probing helicity by purely electrical means without requiring spin detection, application of magnetic materials or magnetic fields. In the considered setup a tilt of the spin orientation with respect to the normal of the sample leads to a reduction in the two-terminal conductance with current-voltage characteristics and temperature dependence typical of Luttinger liquid constrictions.