QUANTUM BEATS BETWEEN EXCITONS AND BIEXCI TONS LOCALIZED IN TERNARY CRYSTALS OF CDSXSE1-X

The phase and energy relaxation of the localized electronic states has been studied in CdSxSe1-x, mixed crystals with femtosecond pulses. Un der resonant excitation, at 2K, the phas;e coherence of the localized excitons lasts several tens of picoseconds. Both phonon assisted inter well tunneling and interband radiative recombination are involved in t his long decay. Before these processes, a coupling between localized e xcitons in a same well occurs, leading to the formation of biexcitons associated to a much faster decay time (similar to 700 fs). A detailed analysis of the dephasing mechanism due to one and two particle proce sses is performed via the observation of quantum beats between the loc alized excitonic and biexcitonic states.