Phase diagram for the exciton Mott transition in infinite-dimensional electron-hole systems

To understand the essence of the exciton Mott transition in three-dimensional electron-hole systems, the metal-insulator transition is studied for a two-band Hubbard model in infinite dimensions with interactions of electron-electron (hole-hole) repulsion U and electron-hole attraction -U′. By using the dynamical mean-field theory, the phase diagram in the U-U′ plane is obtained (which is exact in infinite dimensions) assuming that electron-hole pairs do not condense. When both electron and hole bands are half-filled, two types of insulating states appear: the Mott-Hubbard insulator for U>U′ and the biexciton-like insulator for U