Институт теоретической физики им. Л.Д. Ландау РАН
L.D. Landau Institute for Theoretical Physics RAS
Research in superconductivity and beyond Gerasim Eliashberg memorial conference
August, 23-26, 2021
Activating superconductivity in a repulsive system by high-energy degrees of freedom
Date/Time: 19:30 25-Aug-2021
This talk will discuss superconducting pairing in a narrow conduction band sandwiched between unoccupied and occupied bands, an arrangement that enables an unconventional pairing mechanism governed by Coulomb repulsion. Pairing interaction originates from repulsion-assisted scattering between far-out pair states in the higher-energy bands and those at the Fermi level. Optimizing the bandstructure design and carrier density in order to bring plasma frequency below the bandgap renders the repulsion unscreened for the processes with a large frequency transfer. This allows the pairing to fully benefit from the pristine Coulomb repulsion strength. The repulsion-induced attraction is particularly strong in two dimensions and is assisted by a low density of carriers and the resulting low plasma frequency values. We will consider possible connections of this mechanism to superconductivity in magic-angle twisted bilayer graphene where the bandstructure features wide dispersive upper and lower minibands. A simple model will be introduced to illustrate the importance of the far-out pairs in these bands and describe testable signatures of this superconductivity mechanism.
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