Acoustic-phonon-mediated superconductivity in Bernal bilayer graphene

TL;DR

This paper develops a comprehensive theory of acoustic-phonon-mediated superconductivity in Bernal bilayer graphene, explaining experimental observations and predicting new superconducting regimes driven by phonons.

Contribution

It introduces a detailed theoretical model that accounts for Coulomb interactions and predicts phonon-induced superconductivity, including specific pairing symmetries and critical temperatures.

Findings

Degenerate $s$-wave and $f$-wave pairings predicted

Superconductivity with $T_c\,\sim 20$ mK near specific doping levels

Superconductivity predicted for broader doping regimes

Abstract

We present a systematic theory of acoustic-phonon-mediated superconductivity, which incorporates Coulomb repulsion, explaining the recent experiment in Bernal bilayer graphene under a large displacement field. The acoustic-phonon mechanism predicts that $s$-wave spin-singlet and $f$-wave spin-triplet pairings are degenerate and dominant. Assuming a spin-polarized valley-unpolarized normal state, we obtain $f$-wave spin-triplet superconductivity with a $T_c\sim 20$ mK near $n_e=-0.6\times 10^{12}$ cm$^{-2}$ for hole doping, in approximate agreement with the experiment. We further predict the existence of superconductivity for larger doping in both electron-doped and hole-doped regimes. Our results indicate that the observed spin-triplet superconductivity in Bernal bilayer graphene arises from acoustic phonons.