Acoustic-phonon-mediated superconductivity in Bernal bilayer graphene
Yang-Zhi Chou, Fengcheng Wu, Jay D. Sau, S. Das Sarma
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 ${T}_{c}\ensuremath{\sim}20$ mK near ${n}_{e}=\ensuremath{-}0.6\ifmmode\times\else\texttimes\fi{}{10}^{12} {\mathrm{cm}}^{\ensuremath{-}2}$ 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.