Efficient charge pumping in graphene

We investigate a graphene quantum pump, adiabatically driven by two thin potential barriers vibrating around their equilibrium positions. For the highly doped leads, the pumped current per mode diverges at the Dirac point due to the more efficient contribution of the evanescent modes in the pumping process. The pumped current shows an oscillatory behavior with an increasing amplitude as a function of the carrier concentration. This effect is in contrast to the decreasing oscillatory behavior of a similar normal pump (i.e. a pump based on a two-dimensional electron gas). The graphene pump driven by two vibrating thin barriers operates more efficiently than the graphene pump driven by two oscillating thin barriers. (paper)