Harnessing the giant out-of-plane Rashba effect and the nanoscale persistent spin helix via ferroelectricity in SnTe thin films

TL;DR

This paper demonstrates how ferroelectricity in SnTe thin films can generate a giant out-of-plane Rashba effect and a nanoscale persistent spin helix, enabling electric control of spin states for advanced spintronic devices.

Contribution

It introduces a novel approach to harness ferroelectricity in SnTe films to achieve a giant out-of-plane Rashba effect and nanoscale persistent spin helix for spintronics.

Findings

Giant out-of-plane Rashba spin-orbit field observed in SnTe thin films.

Reversible ferroelectric switching controls the spin helix orientation.

Potential for nanoscale, electrically tunable spintronic devices.

Abstract

A non-vanishing electric field inside a non-centrosymmetric bulk crystal transforms into a momentum- dependent magnetic field, namely, a spin-orbit field (SOF). SOFs are of great use in spintronics because they enable spin manipulation via the electric field. At the same time, however, spintronic applications are severely limited by the SOF, as electrons traversing the SOF easily lose their spin information. Here, we propose that in-plane ferroelectricity in (001)-oriented SnTe thin films harness the Janus-faced SOF in a reconcilable way to enable electrical spin controllability and suppress spin dephasing. The in-plane ferroelectricity produces a unidirectional out-of-plane Rashba SOF that can host a long-lived helical spin mode known as a persistent spin helix (PSH). Through direct coupling between the inversion asymmetry and the SOF, the ferroelectric switching reverses the out-of-plane Rashba SOF, giving rise to a maximally field-tunable PSH. Furthermore, the giant out- of-plane Rashba SOF seen in the SnTe thin films is linked to the nano-sized PSH, potentially reducing spintronic device sizes to the nanoscale. We combine the two ferroelectric-coupled degrees of freedom, longitudinal charge and transverse PSH, to design intersectional electro-spintronic transistors governed by non-volatile ferroelectric switching within nanoscale lateral and atomic-thick vertical dimensions.