“…32 The temperature of the carrier subsystem is much higher than the lattice temperature and within ∼150 fs 15,17,21 loses a significant part of energy through carrier−phonon intraband scattering, creating, in turn, a nonequilibrium population of hot optical phonons. Very recently, Pogna et al 30 using a variety of time-resolved experimental techniques showed that electrons with proper energy coupled to optical phonons decaying, through certain relaxation channels, to lower energy phonons via anharmonic interactions.…”