Exciton Mott transition and pair condensation in electron-hole systems: Dynamical mean-field theory

The exciton Mott transition and electron-hole (e-h) pair condensation are studied using a two-band Hubbard model with both repulsion and attraction. With the use of the dynamical mean-field theory, we clarify the phase diagram for the phase transitions at zero and finite temperatures. Away from half-filling we find an exciton insulating phase, which is followed by the formation of incoherent e-h pairs, and the first-order transition between a metallic phase and the exciton insulating phase. We also examine the transition temperature to an e-h pair condensed phase where BEC-BCS crossover takes place, and discuss characteristic features of the finite-temperature phase diagram.