Dynamical T‐matrix theory for high‐density excitons in coupled quantum wells

Excitons in coupled quantum wells open the possibility to reach high densities close to equilibrium. In a recent experiment employing a lateral trap potential, a blue shift and a broadening of the exciton emission line has been seen [D. W. Snoke et al., Solid State Commun. 134, 37 (2005)]. The standard Hartree–Fock treatment can explain the blue shift but fails to give a finite broadening. Starting from the (spin‐dependent) many‐exciton Hamiltonian with direct and exchange potential, we present a dynamical T‐matrix calculation for the single‐exciton Green's function which is directly related to the frequency‐ and angle‐resolved photoluminescence. The calculated spectrum is blue shifted and broadened due to exciton–exciton scattering. At high excitation, both the spectrum and the angular emission are getting narrow. This is a direct manifestation for off‐diagonal long range order and a precursor of condensation. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)