Pairing in magic-angle twisted bilayer graphene: Role of phonon and plasmon umklapp

Abstract

The pairing mechanism in twisted bilayer graphene (TBG) remains a central question, which is often contrasted with pairing in other strong-coupled superconductors. However, TBG is unique in many ways. Its phonon dispersion contains many minioptical bands with frequencies exceeding the electronic bandwidth. Here, the authors develop a theory of electronic pairing resulting from this complex phonon structure and find that it mediates stronger interaction, compared to a purely electronic plasmonic mechanism. They also predict experimental signatures of both phonon umklapp and plasmon pairing mechanisms.