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 $p\approx 2\times {10}^{11}{\mathrm{cm}}^{-2}$ and $E_{\perp }\approx -2\times {10}^5$ V/m, the magnetoresistance along $\langle 01\overline{1}\rangle$ greatly exceeds that along $\langle 011\rangle$, 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.

• Received 7 March 2019

DOI:https://doi.org/10.1103/PhysRevB.99.195420