Anomalous Thermoelectric Transport of Dirac Particles in Graphene

We report a thermoelectric study of graphene in both zero and applied magnetic fields. As a direct consequence of the linear dispersion of massless particles, we find that the Seebeck coefficient S-xx diverges with 1/root|n(2D)|, where n(2D) is the carrier density. We observe a very large Nernst signal S-xy (similar to 50 mu V/K at 8 T) at the Dirac point, and an oscillatory dependence of both S-xx and S-xy on n(2D) at low temperatures. Our results underscore the anomalous thermoelectric transport in graphene, which may be used as a highly sensitive probe for impurity bands near the Dirac point.