Dresden 2011 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 42: Graphene II
O 42.5: Vortrag
Mittwoch, 16. März 2011, 12:15–12:30, WIL B321
Electronic structure of graphene twist stacks — •Sam Shallcross1, Sangeeta Sharma2, and Oleg Pankratov1 — 1Lehrstuhl fur Theoretische Festkorperphysik, Staudstr. 7-B2, 91058 Erlangen, Germany. — 2Max-Planck Institute for Microstructure Physics, Weinberg 2, 06120 Halle, Germany.
We present a study of graphene stacks consisting of an ordered sequence of pairs of twisted layers - the graphene twist stack; extending previous work on the graphene twist bilayer [1,2]. We find that this remarkable system entails a fundamental mixing of dimensionalities: while the twist stack spectrum is generated by an ensemble of independent effective twist bilayer Hamiltonians, the wavefunctions are products of bilayer wavefunctions and standing electron waves in the stacking direction, and thus extend over many layers of the stack. These have the property that of the ensemble of Dirac cones that constitute the twist stack band structure, it is those topologically closest to single layer graphene that dominate the surface region. We further examine the impact of stacking disorder, finding that these results are robust for moderate stacking fault density. With these results we are able to explain some of the striking differences between the physics of graphene grown on the C-face of SiC, and the by now well studied model of this system, the graphene twist bilayer.
[1] S. Shallcross, S. Sharma, E. Kandelaki, and O. A. Pankratov, Phys. Rev. B, 81:165105, 2010.
[2] S. Shallcross, S. Sharma, and O. A. Pankratov, Phys. Rev. Lett., 101:056803, 2008.