Raman Scattering in Quantum Disks: Enhanced Efficiency of the Electron-phonon Interaction Due to Non-adiabaticity

We treat resonant Raman scattering via the multiphonon exciton transitions in cylindrical quantum dots with a parabolic confinement in the lateral direction and with a finite rectangular interface-barrier confinement in the axial direction. The optical phonons and the electron-phonon interaction are considered within the multimode dielectric model. The model exploits both electrostatic and mechanical boundary conditions for the relative ionic displacement vector, as well as the phonon spatial dispersion in bulk. The confined phonon modes in a quantum dot are hybrids of bulk-like and interface vibrations. Raman spectra, calculated using the multimode dielectric model, compare well with experimental data. Multiphonon Raman amplitudes are calculated taking into account the effects of non-adiabaticity, which play a crucial role in the optical spectra of quantum dots. Peak intensities of Raman spectra are investigated as a function of the confinement frequency parameter and of the height of a quantum dot. Non-adiabatic transitions are shown to strongly increase the scattering probabilities and the relative multiphonon scattering intensities with respect to the one-phonon intensity.