BUILDUP AND DECOHERENCE OF OPTICAL TRANSIENTS IN DISORDERED SEMICONDUCTORS

For a model two-band semiconductor with static disorder, suddenly illu minated by intense light, the averaged non-equilibrium Green function can be obtained within the coherent potential approximation. Explicit solutions found previously are analyzed on numerical examples of the t ransient photoexcited distribution. The results are used to test the s emigroup property of the propagators and the analogous factorization o f the particle correlation function known as the generalized Kadanoff- Baym ansatz. Both properties hold much better if quasiparticle states are used instead of the bare particles. The quasiparticle modification of the ansatz is motivated formally and verified on numerical data.