Electron spectrum of epitaxial graphene monolayers

TL;DR

This paper investigates the electron spectrum of epitaxial graphene on SiC, revealing substrate-dependent modifications to the Dirac cone and implications for electron mobility.

Contribution

It derives a modified Dirac-Weyl Hamiltonian for epitaxial graphene considering substrate effects using ab initio calculations and symmetry analysis.

Findings

Dirac cone remains nearly intact on C-face

Band splitting of about 30 meV on Si-face

Resonant interaction with interface states affects mobility

Abstract

Epitaxial graphene on SiC possesses, quite remarkably, an electron spectrum similar to that of freestanding samples. Yet, the coupling to the substrate, albeit small, affects the quasiparticle properties. Combining \emph{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.