Acoustic-phonon-mediated superconductivity in moireless graphene multilayers

We investigate the competition between acoustic phonon mediated superconductivity and the long-range Coulomb interaction in moireless graphene multilayers, specifically, Bernal bilayer graphene, rhombohedral trilayer graphene, and ABCA-stacked tetralayer graphene. In these graphene multilayers, the acoustic phonons can realize, through electron-phonon coupling, both spin-singlet and spin-triplet pairings, and the intra-sublattice pairings (s-wave spin-singlet and f-wave spin-triplet) are the dominant channels. Our theory naturally explains the distinct recent experimental findings in Bernal bilayer graphene and rhombohedral trilayer graphene, and we further predict the existence of superconductivity in ABCA tetralayer graphene arising from electron-phonon interactions. In particular, we demonstrate that the acoustic phonon mediated superconductivity prevails over a wide range of doping in rhombohedral trilayer graphene and ABCA tetralayer graphene while superconductivity exists only in a narrow range of doping near the Van Hove singularity in Bernal bilayer graphene. Key features of our theory are the inclusion of realistic band structures with the appropriate Van Hove singularities and Coulomb repulsion effects (the so-called mu* effect) opposing the phonon-induced superconducting pairing. We also discuss how intervalley scatterings can suppress the spin-triplet spin-polarized superconductivity. Our work provides detailed prediction based on electron-acoustic phonon interaction induced graphene superconductivity, which should be investigated in future experiments.

Automated summary

We investigate the competition between acoustic phonon mediated superconductivity and the long-range Coulomb interaction in moireless graphene multilayers. Our theory explains recent experimental findings in Bernal bilayer graphene and rhombohedral trilayer graphene, and predicts the existence of superconductivity in ABCA tetralayer graphene. The inclusion of realistic band structures with Van Hove singularities and Coulomb repulsion effects in our theory is crucial. Our work provides detailed predictions for graphene superconductivity induced by electron-acoustic phonon interaction, which should be investigated in future experiments.