Many‐Body Theory for the Dense Exciton Gas of Direct Semiconductors II. Calculation of Exciton Level Shift and Damping in Dependence on Exciton Density

The spectral properties of a dense exciton gas are discussed using an exciton self‐energy in second collisional Born approximation with respect to exciton‐exciton interaction. The shift of the continuum edge and the ls exciton as well as the increase of the damping of the ls exciton are calculated linearly in the exciton density. The distribution of ls excitons is assumed to be either a macro‐occupation of the k = 0 state or a Boltzmann distribution with effective temperature varying between 10 and 60 K. A weakening of the level shift is obtained with increasing temperature. In the case of macro‐occupation damping is calculated self‐consistently resulting in a sublinear dependence on density.