Dresden 2011 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 51: Graphene III

O 51.9: Vortrag

Mittwoch, 16. März 2011, 17:00–17:15, WIL B321

Electron spectrum of epitaxial graphene monolayers — •Oleg Pankratov, Stephan Hensel, and Michel Bockstedte — Lst. Theoretische Festkörperphysik, Universität Erlangen, Staudtstr 7B2, 91058 Erlangen.

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, should affect the quasiparticle properties. Whether the graphene-substrate interaction opens an energy gap has been a long debate with experimental estimates ranging from 0 to 0.3 eV [1,2]. Using symmetry analysis, we derive a modified Dirac-Weyl Hamiltonian for graphene epilayers [3]. To determine the numerical values of the Hamiltonian parameters we performed ab initio calculations for a model (5×5) comensurable interface structure. We find that for the epilayer on the C-face the Dirac cone remains intact, whereas 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.

[1] T. Seyller et al., Phys. Status Solidi B 245, 1436 2008

[2] S. Y. Zhou et al., Nature Mater. 6, 770 (2007).

[3] O. Pankratov, S. Hensel, and M. Bockstedte, Phys. Rev. B 82, 121416 (2010).