Berlin 2008 – scientific programme
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O: Fachverband Oberflächenphysik
O 10: Semiconductor Substrates: Epitaxy and Growth
O 10.14: Talk
Monday, February 25, 2008, 16:30–16:45, MA 042
Graphene band structure near the Dirac point - lifting of the degeneracy ? — Eli Rotenberg1, Aaron Bostwick1, Taisuke Ohta1,2, Jessica McChesney1,2, Thomas Seyller3, and •Karsten Horn2 — 1Advanced Light Source, Lawrence Berkeley Lab, California USA — 2Fritz-Haber-Institut der MPG, Berlin — 3Institut für Physik der Kondensierten Materie, Universität Erlangen
The band structure of graphene exhibits a degeneracy of the valence and conduction bands where the linearly dispersing bands cross at the Brillouin zone boundary [1]. In contrast to previous experimental evidence which strongly supports this band crossing, recent photoemission data by Zhou et al. [2] suggest that this degeneracy is lifted in graphene layers on SiC(0001), through the influence of the substrate, and that a band gap opens at the crossing point. We discuss these results in the light of additional results and present a straightforward and rather intuitive explanation for the conflicting results in terms of the quality of the graphene films prepared on silicon carbide.
[1] J.C.Slonczewski and P.R.Weiss, Phys. Rev. 109, 272(1958). [2] A.Boswick et al., Nature Physics 3, 36(2007). [3] S.Y.Zhou et al., Nature Materials 6, 774(2007).