Electron-electron Interaction and Thermoelectricity in Graphene

In this presentation, we report thermoelectric power (TEP) measurements on graphene samples deposited on hexagonal boron nitride substrates where drastic suppression of disorder is achieved. Our results show that at high temperatures where the inelastic scattering rate due to electron-electron (e-e) interactions is higher than the disorder induced elastic scattering rate,~ the measured TEP deviates from the Mott relation, and can be explained by a non-relativistic hydrodynamic flow of electrons. We also investigated TEP in the quantum Hall regime at a high magnetic fields, where we observed symmetry broken integer quantum Hall due to the strong e-e interactions. The field dependence of TEP at these states reveals the important role that exchange interactions play.