Regensburg 2013 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 3: Graphene: Magnetic Fields (jointly with DS, HL, MA, and TT)

O 3.4: Vortrag

Montag, 11. März 2013, 10:15–10:30, H17

Electronic structure of graphene twist flakes — •Wolfgang Landgraf, Sam Shallcross, Karla Türschmann, Dominik Weckbecker, and Oleg Pankratov — Lehrstuhl für Theoretische Festkörperphysik, Staudtstraße 7, D-91058 Erlangen

We study the electronic structure of bilayer graphene flakes with mutually rotated layers. The twist induces a large scale superstructure, a so called moiré pattern, which is a regular array of AA and AB stacked regions. We find that at low energies the electrons are trapped in the AA regions. This feature is visible even for a flake hosting a single AA moiré spot, which is thus acting as a quantum well. The electron density fluctuations induced by the moiré lattice are significant, being an order of magnitude greater than those generated by the rippling of a suspended graphene sheet. Finally, we determine the electronic properties of the twisted graphene flakes in the presence of an external magnetic field. We find a novel "zero-mode" structure, as well as Landau states that exhibit an electron current circulating between two graphene layers of the flake. The current distribution can be visualized as an electron flow on a torus circumventing the AA spot of the moiré lattice.