Interlayer Thermal Coupling of Hot Dirac Fermions in Epitaxial Graphene

Degenerate and nondegenerate ultrafast pump-probe spectroscopy is used to study interlayer thermal coupling of hot Dirac Fermions in carbon face epitaxial graphene. The hot carriers in lightly doped and undoped graphene layers are selectively excited by the pump laser while leaving the carriers in the heavily doped layer not directly excited. Within the 500fs, carries at elevated temperature in the heavily doped layer is observed, which is excited due to the interlayer thermal coupling of the hot carriers.