Polaron in a spherical quantum dot embedded in a nonpolar matrix

Effects of LO phonons for an electron, confined in a spherical quantum dot embedded in a nonpolar matrix, are studied theoretically. A variational method is used to calculate the polaron energy shift by taking into account the interaction with both the bulk type and the interface type phonons in the system. The combination of the adiabatic and the intermediate coupling methods is developed to provide the results, being valid for the wide range of the dot radius and the electron-phonon coupling strength. The method is applied to GaAs, CdSe, and CuCl quantum dots and the results are discussed in comparison with the second-order perturbation theory and other published theories. General properties of a polaron are also calculated and discussed by changing physical parameters, which characterize the system. It is shown that (i) with the increase in the dot radius the magnitude of the polaron energy shift decreases rapidly from large value and then approaches gradually to the bulk value, and (ii) the bulk type LO phonon has the dominant role for the polaron effects and the contribution of interface LO phonon is very small.