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 $1/\sqrt{|n_{2\mathrm{D}}|}$, where $n_{2\mathrm{D}}$ is the carrier density. We observe a very large Nernst signal $S_{xy}$ ($\sim 50\mu \mathrm{V}/\mathrm{K}$ at 8 T) at the Dirac point, and an oscillatory dependence of both $S_{xx}$ and $S_{xy}$ on $n_{2\mathrm{D}}$ 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.

• Received 12 December 2008

DOI:https://doi.org/10.1103/PhysRevLett.102.166808