Exciton–exciton interaction in coupled quantum wells

The exciton–exciton interaction is investigated for spatially indirect excitons in coupled quantum wells. The Hartree–Fock and Heitler–London approaches are improved by a full two-exciton calculation including the van der Waals effect. Using these potentials for the singlet and triplet channel, the two-body scattering matrix is calculated and employed to derive a modified relation between exciton density and blue shift. Such a relation is of central importance for gauging exciton densities on the way toward Bose condensation.