Exchange interaction and phonon confinement in CdSe quantum dots

The fine structure of the lowest (1S(3/2), 1s(e)) electron-hole pair state has been studied for CdSe quantum dots embedded in glass and with sizes R<a(B). Besides the very narrow peaks from the exchange-split lowest pair states (full width at half maximum of 2 meV), two additional structures have been found in luminescence and assigned to confined acoustic photons. The observation of discrete acoustic phonons in the emission spectra verifies the importance of low-frequency acoustic phonons for energy relaxation in quantum dots. The size dependence of the different peaks has been determined and compared with theoretical models.