Exciton-phonon coupled states in CuCl quantum cubes - art. no. 033307

The size dependence of excitonic states and vibrational modes in CuCl cubic quantum dots embedded in NaCl crystals was studied by means of site-select ive persistent spectral hole burning spectroscopy. It is shown that the int eraction of the longitudinal optical (LO) phonon with the exciton results i n the formation of coupled exciton-phonon modes when the energy of the LO p honon approaches the energy spacings between the ground and excited states of the exciton. The energy anticrossings of the LO phonon modes with two hi gher optically allowed excited states of the exciton in CuCl QD's were clea rly observed at confinement energies of about 10 and 6 meV, respectively. I n addition, the linewidth of the LO phonon sideband in CuCl QD's in NaCl cr ystals was found to increase abruptly from 0.3 meV to about 1.2 meV at a co nfinement energy of about 23 meV, which appears to result from the exciton- phonon mixing of the LO phonon mode with the first excited state of the exc iton. The experimental results are qualitatively understood by the LO phono n renormalization theory.