Density-matrix description of frequency-resolved secondary emission from quantum wells

The frequency-resolved secondary emission from excitons in a single 8 nm-wide quantum well is investigated using speckle analysis. We model these experiments starting with a Hamiltonian in the basis of disorder eigenstates of excitons, interacting both with light and acoustical phonons. The distinction between incoherent and coherent secondary emission is intimately related with the decomposition of a two-time exciton density-matrix into a diagonal, incoherent part and a product of polarizations. The latter gives rise to speckling (intensity variations over observation angle), and is called resonant Rayleigh scattering. The results of our simulation agree pretty well with the experimental data and allow a determination of the coherent and incoherent exciton distributions