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TT: Fachverband Tiefe Temperaturen

TT 14: Graphene

TT 14.12: Vortrag

Montag, 1. April 2019, 18:15–18:30, H22

Influence of minivalleys and Berry curvature on electrostatically induced nanostructures in gapped bilayer graphene — •Angelika Knothe and Vladimir Fal’ko — National Graphene Institute, University of Manchester, United Kingdom

We theoretically investigate the properties electrostatically confined nanostructures in gapped bilayer graphene (BLG). We show how the spectrum of subbands in a quantum wire in gapped BLG, and the energy levels in a quantum dot, manifest the minivalley structure and Berry curvature via the associated magnetic moment of the states in the low-energy bands. These features determine the degeneracies of the low-energy minibands / -levels and their valley splitting, which develops linearly in a weak magnetic field. In a quantum point contact, magneto-conductance reflects such degeneracies in the heights of the first conductance steps which develop upon the increase of the channel doping: 8e²/h steps in a wide channel in BLG with a large gap, 4e²/h steps in narrow channels, all splitting into a staircase of 2e²/h steps upon lifting valley degeneracy by a magnetic field B. For quantum dots, we investigate how optical selection rules are influenced by the minivalleys and the orbital magnetic moment, as well as by shapes of the confinement.

References: A. Knothe and V. Fal’ko, Phys. Rev. B 98, 155435 (2018); H. Overweg, A. Knothe, V. I. Fal’ko, K. Ensslin, T. Ihn, et al., arXiv:1809.01920; R. Kraft, I.V. Krainov, V. Gall, A.P. Dmitriev, R. Krupke, I.V. Gornyi, R. Danneau, arXiv:1809.02458