Coulomb interaction, phonons, and superconductivity in twisted bilayer graphene

Tommaso Cea; Francisco Guinea

doi:10.1073/pnas.2107874118

Coulomb interaction, phonons, and superconductivity in twisted bilayer graphene

Proc Natl Acad Sci U S A. 2021 Aug 10;118(32):e2107874118. doi: 10.1073/pnas.2107874118.

Authors

Tommaso Cea^{1

2}, Francisco Guinea^{3

4

5}

Affiliations

¹ IMDEA Nanoscience, 28015 Madrid, Spain.
² Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Científicas, 28049 Madrid, Spain.
³ IMDEA Nanoscience, 28015 Madrid, Spain; paco.guinea@imdea.org.
⁴ Donostia International Physics Center, 20018 San Sebastián, Spain.
⁵ Ikerbasque Basque Foundation for Science, 48009 Bilbao, Spain.

Abstract

The polarizability of twisted bilayer graphene, due to the combined effect of electron-hole pairs, plasmons, and acoustic phonons, is analyzed. The screened Coulomb interaction allows for the formation of Cooper pairs and superconductivity in a significant range of twist angles and fillings. The tendency toward superconductivity is enhanced by the coupling between longitudinal phonons and electron-hole pairs. Scattering processes involving large momentum transfers, Umklapp processes, play a crucial role in the formation of Cooper pairs. The magnitude of the superconducting gap changes among the different pockets of the Fermi surface.

Keywords: graphene; superconductivity; twisted.