Evidence Of Fermi Level Pinning At The Dirac Point In Epitaxial Multilayer Graphene

We investigate the temperature-dependent conductivity of epitaxial multilayer graphene using THz timedomain spectroscopy and find evidence that the Fermi level in quasineutral graphene layers is pinned at the Dirac point by midgap states. We demonstrate that the scattering mechanisms result from the interplay between midgap states that dominate in the vicinity of the Dirac point and short-range potentials that govern at higher energies (>8 meV). Our results highlight the potential of multilayer epitaxial graphene for probing low-energy Dirac particles and also for THz optics.