Charge Transport and Inhomogeneity near the Charge Neutrality Point in Graphene
Abstract
The magnetic field-dependent longitudinal and Hall components of the resistivity rhoxx(H) and rhoxy(H) are measured in graphene on silicon dioxide substrates at temperatures from 1.6 K to room temperature. At charge densities near the charge-neutrality point rhoxx(H) is strongly enhanced and rhoxy(H) is suppressed, indicating nearly equal electron and hole contributions to the transport current. The data are inconsistent with uniformly distributed electron and hole concentrations (two-fluid model) but in excellent agreement with the recent theoretical prediction for inhomogeneously distributed electron and hole regions of equal mobility. At low temperatures and high magnetic fields rhoxx(H) saturates to a value ~h/e2, with Hall conductivity << e2/h, which may indicate a regime of localized v = 2 and v = -2 quantum Hall puddles.