Chiral triplet superconductivity on the graphene lattice

Motivated by the possibility of superconductivity in doped graphene sheets, we investigate superconducting order in the extended Hubbard model on the two-dimensional graphene lattice using the variational cluster approximation (VCA) and the cellular dynamical mean-field theory (CDMFT) with an exact diagonalization solver at zero temperature. The nearest-neighbor interaction is treated using a mean-field decoupling between clusters. We compare different pairing symmetries, singlet and triplet, based on short-range pairing. VCA simulations show that the real (nonchiral), p-triplet wave symmetry is favored for small V, small onsite interaction U, or large doping, whereas the chiral combination p+ip is favored for larger values of V, stronger onsite interaction U, or smaller doping. CDMFT simulations confirm the stability of the p+ip solution, even at half-filling. Singlet superconductivity (extended s wave or d wave) is either absent or subdominant.