Spin-polarized superconductivity from excitonic Cooper pairs

Abstract: We present a theory of spin-polarized superconductivity from the condensation of excitonic Cooper pairs, which are charge-$2e$ bosonic quasiparticles made of Cooper pairs strongly hybridized with excitons. By solving a model of spin-polarized electrons using the strong-coupling expansion to the second order, we demonstrate the emergence of excitonic Cooper pairs from electron-hole fluctuations upon doping a strongly correlated insulator. We characterize their binding energy, effective mass, and the resulting superconducting transition temperature. We propose possible realization of spin-polarized superconductivity in twisted semiconductors with honeycomb moir\'e superlattice.