Homogeneity of bilayer graphene

We present non-linear transport measurements on suspended, current annealed bilayer graphene devices. Using a multi-terminal geometry we demonstrate that devices tend to be inhomogeneous and host two different electronic phases next to each other. Both of these phases show gap-like features of different magnitude in non-linear transport at low charge carrier densities, as already observed in previous studies. Here, we investigate the magnetic field dependence and find that both features grow with increasing field, the smaller one with 0.6 meV/T, the larger one with a 5–10 times higher field dependence. We attribute the larger of the two gaps to an interaction induced broken symmetry state and the smaller one to localization in the more disordered parts of the device.

► We investigate current annealed, suspended bilayer graphene in a Hall cross geometry.
► We show that current annealing cleans the bilayer graphene inhomogeneously.
► The sample centre hosts a clean phase that shows an interaction induced gap.
► A disordered, conducting phase at the sample borders is suppressed by magnetic field.
► The clean phase does not couple to the contacts and might have edge-states.