Quantum Hall Valley Nematics

TL;DR

Quantum Hall valley nematics are interaction-driven topological phases in 2D electron gases under strong magnetic fields, characterized by spontaneous symmetry breaking and sensitive to disorder, with implications for transport and spectroscopy.

Contribution

This review introduces the concept of quantum Hall valley nematics, highlighting their symmetry-breaking mechanisms and potential experimental realizations.

Findings

Quantum Hall valley nematics exhibit spontaneous point-group symmetry breaking.

Topological defects influence charge conduction in these phases.

Disorder impacts the orientational order of the nematic phases.

Abstract

Two-dimensional electron gases in strong magnetic fields provide a canonical platform for realizing a variety of electronic ordering phenomena. Here we review the physics of one intriguing class of interaction-driven quantum Hall states: quantum Hall valley nematics. These phases of matter emerge when the formation of a topologically insulating quantum Hall state is accompanied by the spontaneous breaking of a point-group symmetry that combines a spatial rotation with a permutation of valley indices. The resulting orientational order is particularly sensitive to quenched disorder, while quantum Hall physics links charge conduction to topological defects. We discuss how these combine to yield a rich phase structure, and their implications for transport and spectroscopy measurements. In parallel, we discuss relevant experimental systems. We close with an outlook on future directions.