M. Betz et al., Subthreshold carrier-LO phonon dynamics in semiconductors with intermediate polaron coupling: A purely quantum kinetic relaxation channel, PHYS REV L, 86(20), 2001, pp. 4684-4687
Femtosecond transmission spectra of highly polar CdTe are compared to more
covalent GaAs contrasting semiclassical kinetics with two-time quantum kine
tics based on the Dyson equation. Nonequilibrium heavy holes in CdTe show u
ltrafast energy redistribution via the Frohlich mechanism even if photoexci
ted below the LO phonon energy. This subthreshold relaxation is a genuine q
uantum kinetic effect. It gains importance if the polaron self-energy is co
mparable to the phonon energy. Conservation of the free-particle energies i
s not required under these conditions.