Homogeneous linewidths and confined-phonon sidebands of the resonant exciton luminescence of CuCl quantum dots

We investigated the resonant luminescence spectra of CuCl quantum dots in NaCl and glass matrices with high spectral resolution. The resonant luminescence consists of a sharp zero-phonon line accompanied by Stokes and anti-Stokes sidebands. We confirmed that the sidebands originate from lattice vibrations confined in the quantum dots. The observed ultrasharp homogeneous width of the zero-phonon line indicates a very long phase-relaxation time of the confined excitons at low temperature. The temperature dependence of the homogeneous width is explained by a two-phonon Raman process associated with the confined phonons.