Excitonic and superconducting orders from repulsive interaction on the doped honeycomb bilayer

Abstract

Using a weak-coupling renormalization group formalism, we study competing ordered phases for repulsively interacting fermions on the bilayer honeycomb lattice away from half-filling, which is realized experimentally as doped bilayer graphene. As electrons are added to the system, excitonic order is suppressed, and unconventional superconductivity appears generically in its place. In general it is found that the maximum critical temperature for superconductivity appears directly adjacent to the dome of particle-hole order, illustrating the importance of fluctuations in these channels for the formation of unconventional superconductivity. We obtain the phase diagram showing characteristic ordering temperatures for both short- and long-ranged interactions, and show that the most likely superconducting instabilities occur in $d$-wave, $f$-wave, and pair density wave channels. The nature of and competition between these phases are further analyzed using both free energy expansion and self-consistent mean-field theory. The effects of finite temperature and trigonal warping due to further-neighbor hopping are studied, and implications for experiments on bilayer graphene are discussed.