Tilt-Induced Anisotropic to Isotropic Phase Transition at $\nu = 5/2$

TL;DR

This study investigates how in-plane magnetic fields induce phase transitions in fractional quantum Hall states at filling factors 5/2 and 7/2, revealing a transition from anisotropic to isotropic phases influenced by Landau level mixing.

Contribution

It demonstrates the transition from anisotropic to isotropic compressible phases at high in-plane magnetic fields and links this to Landau level mixing effects.

Findings

In-plane magnetic field destroys fractional quantum Hall states at ν=5/2 and 7/2.

High in-plane fields induce a transition to isotropic compressible phases.

Energy gaps depend unexpectedly on confinement potential width.

Abstract

A modest in-plane magnetic field \Bpar\ is sufficient to destroy the fractional quantized Hall states at $\nu = 5/2$ and 7/2 and replace them with anisotropic compressible phases. Remarkably, we find that at larger \Bpar\ these anisotropic phases can themselves be replaced by isotropic compressible phases reminiscent of the composite fermion fluid at $\nu = 1/2$. We present strong evidence that this transition is a consequence of the mixing of Landau levels from different electric subbands. We also report surprising dependences of the energy gaps at $\nu = 5/2$ and 7/3 on the width of the confinement potential.