Unveiling quantum Hall transport by Efros-Shklovskii to Mott variable range hopping transition with Graphene

TL;DR

This study demonstrates a crossover from Efros-Shklovskii to Mott variable range hopping in graphene's quantum Hall regime, validating VRH as a sufficient conduction model without metallic assumptions.

Contribution

First experimental observation of the crossover between Efros-Shklovskii and Mott VRH regimes in graphene's quantum Hall effect, confirming the Polyakov-Shklovskii scenario.

Findings

Crossover occurs at Hall plateau transitions for large localization lengths

Scaling exponents validate VRH as sole conduction mechanism in quantum Hall regime

No need for metallic conduction assumption on conductance peaks

Abstract

The quantum localization in the quantum Hall regime is revisited using Graphene monolayers with accurate measurements of the longitudinal resistivity as a function of temperature and current. We experimentally show for the first time a cross-over from Efros-Shklovskii Variable Range Hopping (VRH) conduction regime with Coulomb interactions to a Mott VRH regime without interaction. This occurs at Hall plateau transitions for localization lengths larger than the interaction screening length set by the nearby gate. Measurements of the scaling exponents of the conductance peak widths with both temperature and current give the first validation of the Polyakov-Shklovskii scenario that VRH alone is sufficient to describe conductance in the Quantum Hall regime and that the usual assumption of a metallic conduction regime on conductance peaks is unnecessary.