Berlin 2018 – scientific programme

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O: Fachverband Oberflächenphysik

O 27: Graphene: Electronic properties, structure and substrate interaction II (joint session O/TT)

O 27.5: Talk

Tuesday, March 13, 2018, 11:45–12:00, MA 043

A topological edge state in the graphene twist bilayer — •Maximilian Fleischmann, Reena Gupta, Dominik Weckbecker, and Sam Shallcross — Theoretische Festkörperphysik, FAU Erlangen-Nürnberg, Staudtstrasse 7/B2, 91058 Erlangen, Germany

The edge physics of graphene based systems is well known to be highly sensitive to the atomic structure at the boundary, with localized zero mode edge states found only on zigzag type terminations of the lattice. Here we demonstrate that the graphene twist bilayer supports an additional class of topological edge states, that (i) are found for all edge geometries (and thus are robust against edge roughness), (ii) occur at energies coinciding with twist-induced van Hove singularities in the bulk electronic spectrum and possess an electron density strongly modulated by the moiré lattice. Interestingly, these “moiré edge states” exist only for certain lattice commensurations and thus the edge physics of the twist bilayer is, in dramatic contrast to that of the bulk [1], not uniquely determined by the twist angle.

[1] S. Shallcross et al., Phys. Rev. B 87, 245403, 2013.