Phase Space for the Breakdown of the Quantum Hall Effect in Epitaxial Graphene

We report the phase space defined by the quantum Hall effect breakdown in polymer gated epitaxial graphene on SiC (SiC/G) as a function of temperature, current, carrier density, and magnetic fields up to 30 T. At 2 K, breakdown currents (I-c) almost 2 orders of magnitude greater than in GaAs devices are observed. The phase boundary of the dissipationless state (rho(xx) = 0) shows a [1 - (T/T-c)(2)] dependence and persists up to T-c > 45 K at 29 T. With magnetic field Ic was found to increase alpha B-3/2 and T-c alpha B-2. As the Fermi energy approaches the Dirac point, the nu = 2 quantized Hall plateau appears continuously from fields as low as 1 T up to at least 19 T due to a strong magnetic field dependence of the carrier density.