No abstract

In transient laser-induced grating experiments, the diffusion coefficients and lifetimes of free excitons are determined in CdSe at temperatures between 2 and 40 K and for different densities. We find that the diffusion coefficient D decreases and that the recombination lifetime T, increases with increasing temperature. The increase of T& with temperature is due to the release of excitons bound to impurities and to an increase of the radiative lifetime. From the measured D values for motion parallel and perpendicular to the crystal c axis, we extract momentum relaxation rates which are discussed in terms of excitonacoustic-phonon scattering. In pure samples, and for lattice temperatures T (10 K, the interaction via the deformation potential is dominating, while for higher temperatures, the interaction via the piezoelectric potential becomes significant.

 Users may download and print one copy of any publication from the public portal for the purpose of private study or research.  You may not further distribute the material or use it for any profit-making activity or commercial gain  You may freely distribute the URL identifying the publication in the public portal If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.

The nature of the beat modulations observed in nonlinear four-wave mixing in semiconductors is determined by spectral resolution of the time-integrated four-wave-mixing signals. Beats between closelying bound-exciton resonances in CdSe are found to be described by macroscopic polarization interferences between two noninteracting two-level systems. Beats between heavy-hole excitons and light-hole excitons in GaAs quantum wells, on the other hand, are described by a three-level system, i.e. , as a true quantum interference phenomenon.

No abstract