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 (ρ_xx=0) shows a [1-(T/T_c)²] dependence and persists up to T_c>45K at 29 T. With magnetic field I_c was found to increase ∝B^3/2 and T_c∝B². As the Fermi energy approaches the Dirac point, the ν=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.