Quantum Hall ferromagnets, cooperative transport anisotropy, and the random field Ising model

TL;DR

This paper investigates how quantum Hall ferromagnets exhibit transport anisotropy due to domain formation, modeled as a random field Ising system influenced by sample surface roughness, based on recent experimental observations.

Contribution

It introduces a model linking transport anisotropy in quantum Hall systems to domain formation driven by a random field, providing a new interpretation of experimental results.

Findings

Transport anisotropy correlates with domain formation in quantum Hall ferromagnets.

Surface roughness induces a random field that influences domain patterns.

The model explains the temperature dependence of observed anisotropy.

Abstract

We discuss the behaviour of a quantum Hall system when two Landau levels with opposite spin and combined filling factor near unity are brought into energetic coincidence using an in-plane component of magnetic field. We focus on the interpretation of recent experiments under these conditions [Zeitler et al, Phys. Rev. Lett. 86, 866 (2001); Pan et al, Phys. Rev. B 64, 121305 (2001)], in which a large resistance anisotropy develops at low temperatures. Modelling the systems involved as Ising quantum Hall ferromagnets, we suggest that this transport anisotropy reflects domain formation induced by a random field arising from isotropic sample surface roughness.