Probing variations of the Rashba spin-orbit coupling at the nanometer scale

TL;DR

This paper maps the nanometer-scale variations of the Rashba spin-orbit coupling in an InSb inversion layer using scanning tunnelling spectroscopy, revealing strong local fluctuations that impact spintronic device stability.

Contribution

It introduces a novel method to probe the real space pattern of the Rashba parameter at nanometer resolution, advancing understanding of spin-orbit interactions in semiconductors.

Findings

Strong local fluctuations in Rashba coupling correlated with electrostatic potential

Mapping reveals critical fluctuations affecting spintronic device robustness

Large Rashba coefficient (~1 eVÅ) observed in InSb inversion layer

Abstract

The Rashba effect as an electrically tunable spin-orbit interaction is the base for a multitude of possible applications such as spin filters, spin transistors, and quantum computing using Majorana states in nanowires. Moreover, this interaction can determine the spin dephasing and antilocalization phenomena in two dimensions. However, the real space pattern of the Rashba parameter has never been probed, albeit it critically influences, e.g., the more robust spin transistors using the spin helix state and the otherwise forbidden electron backscattering in topologically protected channels. Here, we map this pattern down to nanometer length scales by measuring the spin splitting of the lowest Landau level using scanning tunnelling spectroscopy. We reveal strong fluctuations correlated with the local electrostatic potential for an InSb inversion layer with a large Rashba coefficient (~1 eV{\AA}). The novel type of Rashba field mapping enables a more comprehensive understanding of the critical fluctuations, which might be decisive towards robust semiconductor-based spintronic devices.