Electron-hole coexistence in disordered graphene probed by high-field magneto-transport

We report on magneto-transport measurement in disordered graphene under a pulsed magnetic field of up to 57 T. For large electron or hole doping, the system displays the expected anomalous integer quantum Hall effect (IQHE) specific to graphene down to the filling factor nu = 2. In the close vicinity of the charge neutrality point, the system breaks up into coexisting puddles of holes and electrons, leading to a vanishing Hall and finite longitudinal resistance with no hint of divergence at very high magnetic field. Large resistance fluctuations are observed near the Dirac point. They are interpreted as the natural consequence of the presence of electron and hole puddles. The magnetic field at which the amplitude of the fluctuations is the largest is directly linked to the mean size of the puddles.