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Theory of Phonon-Mediated Superconductivity in Twisted Bilayer Graphene

TitleTheory of Phonon-Mediated Superconductivity in Twisted Bilayer Graphene
Publication TypeJournal Article
Year of Publication2018
AuthorsF. Wu, A.. H. MacDonald, and I. Martin
JournalPHYSICAL REVIEW LETTERS
Volume121
Pagination257001
Date PublishedDEC 17
ISSN0031-9007
Abstract

We present a theory of phonon-mediated superconductivity in near magic angle twisted bilayer graphene. Using a microscopic model for phonon coupling to moire band electrons, we find that phonons generate attractive interactions in both s- and d-wave pairing channels and that the attraction is strong enough to explain the experimental superconducting transition temperatures. Before including Coulomb repulsion, the s-wave channel is more favorable; however, on-site Coulomb repulsion can suppress s-wave pairing relative to d wave. The pair amplitude varies spatially with the moire period, and is identical in the two layers in the s-wave channel but phase shifted by pi in the d-wave channel. We discuss experiments that can distinguish the two pairing states.

DOI10.1103/PhysRevLett.121.257001