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HL: Fachverband Halbleiterphysik

HL 32: Twisted Bilayer Graphene (jointly with DY, MA, HL, DS, O) (joint session TT/HL)

HL 32.6: Vortrag

Dienstag, 17. März 2020, 15:15–15:30, HSZ 201

Fractional quantum Hall states for Moiré superstructures in the Hofstadter regime — •Bartholomew Andrews and Alexey Soluyanov — Department of Physics, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland

We apply a perpendicular magnetic field to the minimal effective two-orbital Fermi-Hubbard model based on a description of the low-energy physics of twisted bilayer graphene at the first magic angle. Through the use of a Peierl's substitution, we determine the Landau level splitting and study the structure of the resulting Chern bands for a range of magnetic flux per plaquette. We identify isolated, topological, and flat bands in the spectrum at low energies. We show that, with the inclusion of a nearest-neighbor density-density interaction, fractional quantum Hall states can be realized solely within these flat bands. Specifically, we characterize the ν = 1/3 Laughlin state through the use of change pumping, spectral flow, entanglement scaling, and CFT edge state counting; and we analyze its dependence on orbital mixing. Ultimately, we comment on the applicability of this model for experiment.