Homogeneous Broadening of the Zero Optical Phonon Spectral Line in Semiconductor Quantum Dots

Two different mechanisms of homogeneous broadening of the zero-optical-phonon spectral line in CdSe nanocrystal quantum dots are analysed. The first mechanism is due to modulation of the optical-phonon mode frequencies. The second one is caused by multiple-acoustic-phonon-assisted transitions. We show that homogeneous broadening due to acoustic phonons dominates at low temperatures and for small nanocrystal radii. For large nanocrystal radii and at room temperature, the two mechanisms become comparable.