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

TL;DR

This paper develops a dynamical T-matrix approach to model high-density excitons in coupled quantum wells, capturing spectral broadening and shifts due to exciton interactions, and indicating signs of exciton condensation.

Contribution

It introduces a dynamical T-matrix calculation for exciton Green's functions that accounts for many-body effects beyond Hartree-Fock, explaining spectral broadening and shifts.

Findings

Spectral blue shift and broadening due to exciton-exciton scattering

Narrowing of spectrum and emission at high excitation

Evidence of off-diagonal long-range order and precursor to condensation

Abstract

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 (Snoke, SSC 134). 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.