Heterostructure Symmetry and the Orientation of the Quantum Hall Nematic Phases

TL;DR

This study investigates how the structural symmetries of GaAs/AlGaAs heterostructures influence the orientation of quantum Hall nematic phases, revealing that the depth of the electron system affects nematic alignment.

Contribution

It demonstrates that the nematic orientation is unaffected by local confinement symmetry but depends on the depth of the 2D electron system at heterointerfaces.

Findings

Nematic orientation is independent of local confinement potential symmetry.

Nematic orientation depends on the depth of the 2D electron system.

Surface proximity does not dictate nematic alignment.

Abstract

Clean two-dimensional electron systems in GaAs/AlGaAs heterostructures exhibit anisotropic collective phases, the quantum Hall nematics, at high Landau level occupancy and low temperatures. An as yet unknown native symmetry-breaking potential consistently orients these phases relative to the crystalline axes of the host material. Here we report an extensive set of measurements examining the role of the structural symmetries of the heterostructure in determining the orientation of the nematics. In single quantum well samples we find that neither the local symmetry of the confinement potential nor the distance between the electron system and the sample surface dictates the orientation of the nematic. In remarkable contrast, for two-dimensional electrons confined at a single heterointerface between GaAs and AlGaAs, the nematic orientation depends on the depth of the two-dimensional electron system beneath the sample surface.