# Orientation of hole quantum Hall nematic phases in an out-of-plane electric field

## TL;DR

This study observes a tunable quantum Hall nematic phase in a 2D hole system, where an out-of-plane electric field controls the orientation of stripe phases, revealing the influence of spin-orbit coupling and Landau level mixing.

## Contribution

It demonstrates electric field control of nematic phase orientation in a 2D hole system, highlighting the role of spin-orbit effects and Landau level mixing in quantum Hall phases.

## Key findings

- Anisotropic resistance state observed at specific hole density and electric field.
- Reversing electric field polarity rotates the stripe orientation by 90°.
- Electric field influences the formation and orientation of quantum Hall nematic phases.

## Abstract

We present observations of an anisotropic resistance state at Landau level filling factor $\nu=5/2$ in a two-dimensional hole system (2DHS), which occurs for certain values of hole density $p$ and average out-of-plane electric field $E_\perp$. The 2DHS is induced by electric field effect in an undoped GaAs/AlGaAs quantum well, where front and back gates allow independent tuning of $p$ and $E_\perp$, and hence the symmetry of the confining potential. For $p\approx2\times10^{11}$~cm$^{-2}$ and $E_\perp \approx -2 \times10^{5}$~V/m, the magnetoresistance along $\langle01\bar1\rangle$ greatly exceeds that along $\langle011\rangle$, suggesting the formation of a quantum Hall nematic or `stripe' phase. Reversing the sign of $E_\perp$ rotates the stripes by $90^{\circ}$. We suggest this behavior may arise from the mixing of the hole Landau levels and a combination of the Rashba and Dresselhaus spin-orbit coupling effects.