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 [11ˉ0] 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.
@article{arxiv.1307.5489,
title = {Theory of Native Orientational Pinning in Quantum Hall Nematics},
author = {Inti Sodemann and Allan H. MacDonald},
journal= {arXiv preprint arXiv:1307.5489},
year = {2013}
}