Phonon interaction of single excitons and biexcitons

Abstract

The exciton-phonon coupling of a single zero-dimensional exciton is studied in epitaxially grown ${\mathrm{C}\mathrm{d}\mathrm{S}\mathrm{e}/\mathrm{Z}\mathrm{n}}_{1-x}{\mathrm{Cd}}_x\mathrm{Se}$ 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 $\sim 3\%$ 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.