Valley polarization effects on the localization in graphene Landau levels

TL;DR

This study explores how disorder and valley polarization influence localization in graphene's Landau levels, revealing anomalous delocalization in the lowest level and partial polarization effects at higher levels.

Contribution

It uncovers the role of valley mixing in anomalous localization and details how disorder affects valley polarization across Landau levels in graphene.

Findings

Disorder can induce wavefunction delocalization in the lowest Landau level.

Valley mixing is the main cause of anomalous localization in the lowest LL.

Disorder induces partial valley polarization in higher Landau levels.

Abstract

Effects of disorder and valley polarization in graphene are investigated in the quantum Hall regime. We find anomalous localization properties for the lowest Landau level (LL), where disorder can induce wavefunction delocalization (instead of localization), both for white-noise and gaussian-correlated disorder. We quantitatively identify the contribution of each sublattice to wavefunction amplitudes. Following the valley (sublattice) polarization of states within LLs for increasing disorder we show: (i) valley mixing in the lowest LL is the main effect behind the observed anomalous localization properties, (ii) the polarization suppression with increasing disorder depends on the localization for the white-noise model, while, (iii) the disorder induces a partial polarization in the higher Landau levels for both disorder models.