Gap opening in the zeroth Landau level of graphene

TL;DR

This paper reports on the observation of a zero-value Hall plateau and increased resistivity at the charge neutrality point in graphene under high magnetic fields, explained by a field-dependent splitting of the zeroth Landau level.

Contribution

It introduces a simple model involving a magnetic field-dependent splitting of the zeroth Landau level to explain the observed transport phenomena in graphene.

Findings

Observation of a zero Hall plateau at high magnetic fields

Resistivity increase at the charge neutrality point

Model reproduces experimental results with spin-split Landau level

Abstract

We have measured a strong increase of the low-temperature resistivity $\rho_{xx}$ and a zero-value plateau in the Hall conductivity $\sigma_{xy}$ at the charge neutrality point in graphene subjected to high magnetic fields up to 30 T. We explain our results by a simple model involving a field dependent splitting of the lowest Landau level of the order of a few Kelvin, as extracted from activated transport measurements. The model reproduces both the increase in $\rho_{xx}$ and the anomalous $\nu=0$ plateau in $\sigma_{xy}$ in terms of coexisting electrons and holes in the same spin-split zero-energy Landau level.