Gap opening in the zeroth Landau level of graphene

Abstract

We have measured a strong increase of the low-temperature resistivity $ρ_{xx}$ and a zero-value plateau in the Hall conductivity $σ_{xy}$ 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 $ρ_{xx}$ and the anomalous $ν=0$ plateau in $σ_{xy}$ in terms of coexisting electrons and holes in the same spin-split zero-energy Landau level.

4 pages, 3 figures