Phonon interaction of single excitons and biexcitons

The exciton-phonon coupling of a single zero-dimensional exciton is studied in epitaxially grown CdSe/Zn1−xCdxSe quantum dot structures by analyzing its linewidth and phonon-assisted recombination. The single excitons do not couple to only a single phonon mode, but to a distribution of phonons, here consisting of the zone-center ZnSe longitudinal optic (LO) phonon and of mixed modes with an energy statistics centered between the ZnSe and CdSe LO phonon. Both exciton and corresponding biexciton reveal LO-phonon replica intensities of ∼3% of the respective zero-phonon emission. These similar LO-phonon coupling strengths are evidence of a reduced polarity of the exciton states within the biexciton as the result of exciton-exciton correlation