Temperature dependence of the quantum Hall effect in graphene

We have measured the temperature dependence of the quantum Hall effect in single layer graphene for temperatures ranging from 4 to 300 K in magnetic fields up to 32 T. The gap between higher Landau levels measured at ν = 6 follows the classically expected behavior for broadened Landau levels. In contrast, the ν = ± 2 gap, corresponding to excitations between the zeroth and first Landau level of electrons and holes, behaves totally different and is strongly temperature and field dependent. At high magnetic fields and T > 100 K it approaches the theoretical gap for very sharp Landau levels.