Exciton-confined-phonon interaction in quantum dots

Sharp line width of excitons in CuCl quantum dots was observed by means of persistent spectral hole burning. At 2 K, the hole spectrum consists of a zero-phonon line (line width = 0.14 meV) and its acoustic phonon wing, and they are well separated from each other. With increasing the temperature T, the zero-phonon hole and its phonon side band are merged into each other and finally the hole spectrum shows broadening. Temperature-dependent hole spectra were compared with a theoretical simulation of the absorption spectra of single-sized dots. Contrary to the usual exciton broadening of the linear temperature dependence, the broadening is proportional to 1/[exp(δ/kT) − 1] at low temperature, where δ is the confined acoustic phonon energy in quantum dots. This observation demonstrates unique characteristics of the exciton-phonon interaction in quantum dots,