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

摘要

Excitons in coupled quantum wells open the possibility to reach highdensities close to equilibrium. In a recent experiment employing a lateral trappotential, a blue shift and a broadening of the exciton emission line has beenseen (Snoke, SSC 134). The standard Hartree-Fock treatment can explain the blueshift but fails to give a finite broadening. Starting from the (spin-dependent)many-exciton Hamiltonian with direct and exchange potential, we present adynamical T-matrix calculation for the single-exciton Green's function which isdirectly related to the frequency- and angle-resolved photoluminescence. Thecalculated spectrum is blue shifted and broadened due to exciton-excitonscattering. At high excitation, both the spectrum and the angular emission aregetting narrow. This is a direct manifestation for off-diagonal long rangeorder and a precursor of condensation.