Theory of Native Orientational Pinning in Quantum Hall Nematics

TL;DR

This paper explains the native orientational pinning of quantum Hall nematic states as arising from Rashba and Dresselhaus spin-orbit interactions, clarifying a long-standing mystery in electron transport anisotropy.

Contribution

It demonstrates that the relative sign of Rashba and Dresselhaus coefficients determines the nematic orientation, providing a theoretical explanation consistent with experiments.

Findings

Pinning direction depends on Rashba and Dresselhaus sign

Theoretical pinning energy matches experimental estimates

Orientation aligns with specific crystallographic directions

Abstract

The orientation of the electron-nematic states discovered in the quantum Hall regime of GaAs $[001]$ growth-direction quantum wells is pinned by a weak native source of anisotropy. In this Letter we explain that this property, which has remained mysterious over more than a decade of research, follows from the presence of both Rashba and Dresselhaus spin-orbit interactions. The hard transport direction of the nematic state is determined by the relative sign of the Rashba and Dresselhaus coefficients, and coincides with either the $[110]$ or the $[1\bar{1}0]$ crystallographic direction. Our theoretical estimate of the pinning energy is in agreement with experimental studies of the competition between native pinning and intentional pinning by an in-plane magnetic field.