Hidden Quantum Hall Stripes in Al$_{x}$Ga$_{1-x}$As/Al$_{0.24}$Ga$_{0.76}$As Quantum Wells

TL;DR

This study reveals hidden quantum Hall stripe phases in AlGaAs quantum wells, which are isotropic and more robust than predicted, differing from conventional stripe phases and absent in ultrahigh mobility GaAs wells.

Contribution

The paper identifies and characterizes hidden quantum Hall stripe phases in AlGaAs quantum wells, expanding understanding of phase robustness and system dependence.

Findings

Hidden QHS phases are isotropic and N-independent.

Stripe phases are more robust than theoretical models suggest.

Hidden QHS phases are absent in ultrahigh mobility GaAs wells.

Abstract

We report on transport signatures of hidden quantum Hall stripe (hQHS) phases in high ($N > 2$) half-filled Landau levels of Al$_{x}$Ga$_{1-x}$As/Al$_{0.24}$Ga$_{0.76}$As quantum wells with varying Al mole fraction $x < 10^{-3}$. Residing between the conventional stripe phases (lower $N$) and the isotropic liquid phases (higher $N$), where resistivity decreases as $1/N$, these hQHS phases exhibit isotropic and $N$-independent resistivity. Using the experimental phase diagram we establish that the stripe phases are more robust than theoretically predicted, calling for improved theoretical treatment. We also show that, unlike conventional stripe phases, the hQHS phases do not occur in ultrahigh mobility GaAs quantum wells, but are likely to be found in other systems.