Special QM Seminar Speaker Bart Andrews (University of Zurich) Friday, February 21, 11 am in 3 LeConte (please note this room change from 325 LeConte)

Time/Venue Friday, February 21, 11 am in 3 LeConte (please note this room change from 325 LeConte)
Host
Mike Zaletel
Title
Fractional quantum Hall states for Moiré superstructures in the
Hofstadter regime
Abstract We present evidence for fractional quantum Hall states in a
recently-proposed Moiré superlattice Hamiltonian, inspired by the
low-energy physics of twisted bilayer graphene at the first magic angle
[Koshino et al., PRX 8, 031087 (2018)]. We apply a perpendicular
magnetic field to the minimal effective two-orbital Fermi-Hubbard model,
through the use a Peierls substitution, so that the system is in the
Hofstadter regime. Subsequently, we determine the Landau level splitting
and study the structure of the Chern bands for a range of magnetic flux
per plaquette. In doing so, we identify topological flat minibands in
the spectrum at low energies, and show that, with the inclusion of a
density-density interaction, fractional quantum Hall states can be
realized solely within these flat bands. We characterize the primary
fractional state through the use of charge pumping, spectral flow,
entanglement scaling, and CFT edge state counting; and comment on its
breakdown transition. Ultimately, we discuss the implications of these
results for experiment, as well as other effective Moiré Hamiltonians.

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