ANHARMONIC RENORMALIZATION AND NON-MARKOVIAN DECAY OF COHERENT OPTICAL PHONONS IN POLAR SEMICONDUCTORS

The influence of anharmonic renormalization effects on the decay dynam ics of coherent longitudinal optical phonons is investigated from a mi croscopic point of view. Time-resolved coherent anti-Stokes Raman sign als are calculated for GaP on the basis of a full phonon dispersion ca lculation, and the relevant decay channels are identified and compared . Anharmonic renormalization effects are found to induce non-Markovian behaviour of the decay dynamics and lead to a decrease of the decay t ime. The renormalization effects only depend on the special properties of the phonon dispersion of the given material. This underlines the i ntrinsic nature of the non-Markovian decay dynamics of phonons for any material. Non-Markovian dynamics of the decay of coherent LO-phonons is calculated for GaP and result in a 30% faster decay signal than the corresponding Markovian dynamics.