Disorder and interactions in quantum Hall ferromagnets: effects of disorder in Skyrmion physics

TL;DR

This study uses Hartree-Fock calculations to explore how disorder and interactions influence the phases of quantum Hall ferromagnets near filling factor 1, revealing transitions from metallic to various insulating and ferromagnetic states.

Contribution

It provides a detailed phase diagram of quantum Hall ferromagnets under disorder, highlighting the evolution of ground states and predicting experimental signatures in transport and NMR.

Findings

Transition from quasi-metallic paramagnet to ferromagnetic insulator with increasing interaction.

Identification of a ferromagnetic Skyrmion quasiparticle glass phase.

Predictions for NMR spectra signatures in different disorder regimes.

Abstract

We present a Hartree-Fock study of the competition between disorder and interactions in quantum Hall ferromagnets near $\nu=1$. We find that the ground state at $\nu=1$ evolves with increasing interaction strength from a quasi-metallic paramagnet, to a partially spin-polarized ferromagnetic Anderson insulator, and to a fully spin-polarized ferromagnet with a charge gap. Away from $\nu=1$, the ground state evolves from a conventional Anderson insulator, to a conventional quasiparticle glass, and finally to a ferromagnetic Skyrmion quasiparticle glass. These different regimes can be measured in low-temperature transport and NMR experiments. We present calculations for the NMR spectra in different disorder regimes.