Phase diagram of electron–hole systems: Interplay between exciton Mott transition and quantum pair condensation

Abstract

Quasi-thermal-equilibrium states of electron–hole (e–h) systems in photoexcited insulators are studied from a theoretical viewpoint, stressing the exciton Bose–Einstein condensation (BEC), the e–h BCS-type pair-condensed state, and the exciton Mott transition between an insulating exciton/biexciton gas phase and a metallic e–h plasma phase. We determine the quasi-equilibrium phase diagram of the e–h system at zero and finite temperatures with applying the dynamical mean-field theory (DMFT) to the e–h Hubbard model with both repulsive and attractive on-site interactions. Effects of inter-site interactions on the exciton Mott transition are also clarified with applying the extended DMFT to the extended e–h Hubbard model.