Evidence of nonperturbative continuum correlations in two-dimensional exciton systems in semiconductor microcavities - art. no. 027402

In nonlinear semiconductor optics, two-particle scattering is often being m odeled successfully within the second Born approximation (2nd BA) of the Co ulomb interaction. It is shown in this paper that, at low energies, such a perturbative treatment of Coulomb correlations applied to exciton-exciton s cattering in two-dimensional systems fails even qualitatively (unless pheno menological or self-consistent dephasing processes are included in the theo ry). We show that the failure of the 2nd BA in two dimensions can be inferr ed from a comparison of our theoretical results with reported experiments o f four-wave mixing signals from semiconductor microcavities.