Statistical mechanics of screened spatially indirect excitons

We study thermodynamic properties of spatially separated electron-hole plasma in double-layered systems using Green function formalism. The screening of the Coulomb interaction is considered in the framework of Thomas-Fermi approximation, and a qualitatively new mechanism of screening by indirect excitons is taken into account. The exciton density is shown to decrease sharply with increasing electron-hole separation up to one exciton Born radius. The strong mutual enhancement of screening and charge-separation effects is found.