Large reduction in hot-carrier energy-loss rates in CdSe caused by nonequilibrium optical phonons

We obtain hot-carrier cooling rates in CdSe using upconversion luminescence with 2.5-psec time resolution. The carrier energy-loss rates are significantly reduced in comparison with those expected in a simple theory of carrier energy transfer to the lattice. The slow cooling can be explained to be caused by hot-phonon effects provided that the lattice dynamical lifetime of optical phonons in CdSe is about 6 ps at 8 K.