Exchange interaction and phonon confinement in CdSe quantum dots

The fine structure of the lowest (1${\mathit{S}}_{3/2}$, 1${\mathit{s}}_{\mathrm{e}}$) electron-hole pair state has been studied for CdSe quantum dots embedded in glass and with sizes R<${\mathit{a}}_{\mathit{B}}$. 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 phonons. 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. © 1996 The American Physical Society.