Theory of exciton dephasing in semiconductor quantum dots

We formulate a theory of exciton dephasing in semiconductor quantum dots extending the Huang-Rhys theory of F centers to include the mixing among the exciton state manifold through the exciton-acoustic-phonon interaction and we identify the mechanisms of pure dephasing. We can reproduce quantitatively the magnitude as well as the temperature dependence of the exciton dephasing rate observed in GaAs quantum dotlike islands. In this system it turns out that both the diagonal and off-diagonal exciton-phonon interactions are contributing to the exciton pure dephasing on the same order of magnitude. Examining the previous data of the exciton dephasing rate in GaAs islands, CuCl and CdSe nanocrystals, we point out the correlation between the temperature dependence of the dephasing rate and the strength of the quantum confinement and we explain the gross features of the temperature dependence in various materials quantum dots. Furthermore, we discuss likely mechanisms of the exciton population decay.