Exciton–optical phonon interaction in a spherical quantum dot embedded in nonpolar matrix

Exciton–optical-phonon system in a spherical quantum dot embedded in a nonpolar matrix is studied with the consideration of the finite potential barrier and the image potential. The lowest energy of an exciton interacting with the bulk-type and the interface-type longitudinal-optical (LO) phonons is calculated by using a variational method. The virtual phonon number is also calculated in order to clarify the involvement of the LO phonon in exciton state. Our results show that with the decrease in the dot radius the LO-phonon effects on an exciton decrease gradually from the bulk value and then increase rapidly after taking the minimum. This is contrasted with the results calculated with the infinite potential barrier, where the monotonic decrease appears.