Electron spectrum of epitaxial graphene monolayers

Epitaxial graphene on SiC possesses, quite remarkably, an electron spectrum similar to that of free-standing samples. Yet, the coupling to the substrate, albeit small, affects the quasiparticle properties. Combining ab initio calculations with symmetry analysis, we derive a modified Dirac-Weyl Hamiltonian for graphene epilayers. While for the epilayer on the C-face the Dirac cone remains almost intact, for epilayers on the Si-face the band splitting is about 30 meV. At certain energies, the Dirac bands are significantly distorted by the resonant interaction with interface states, which should lead to mobility suppression, especially on the Si-face.