PDF Nonequilibrium electron dynamics in pump-probe spectroscopy: Role of excited phonon populations

Nonequilibrium electron dynamics in pump-probe spectroscopy: Role of excited phonon populations

We study the role of excited phonon populations in the relaxation rates of nonequilibrium electrons using
a nonequilibrium Green’s function formalism. The transient modifications in the phononic properties are
accounted for by self-consistently solving the Dyson equation for the electron and phonon Green’s functions. The
pump-induced changes manifest in both the electronic and phononic spectral functions. We find that the excited
phonon populations suppress the decay rates of nonequilibrium electrons due to enhanced phonon absorption.
The increased phonon occupation also sets the nonequilibrium decay rates and the equilibrium scattering rates
apart. The decay rates are found to be time dependent, and this is illustrated in the experimentally observed
population decay of photoexcited Bi1.5Sb0.5Te1.7Se1.3.