Ultrafast breathinglike oscillation in the exciton density of ZnSe quantum wells

2020-03-04 05:00:22

time density phonon coherence Excitonic

责任者: Hui Zhao;Don, B.D.;Schwartz, G.;Kalt, H. 单位: Inst. fur Angewandte Phys., Univ. Karlsruhe, Germany 来源出处: Physical Review Letters(Phys. Rev. Lett. (USA)),2005/04/08,94(13):137402-1 摘要: The spatial density profile of a low-density exciton ensemble in ZnSe quantum wells shows a breathinglike oscillation on a 30-ps time scale. This breathing results from the emission of the first acoustic phonon at the end of the quasiballistic transport phase of the excitons which reverses their direction of propagation. Since the scattering destroys the phase of the excitonic wave function, one can deduce simultaneously the coherence length and the coherence time of excitonic transport by evaluation of the oscillation measured from a single experiment. The breathing, which can be modeled by Monte Carlo simulations, is quenched for rising lattice temperature, i.e., increasing phonon absorption, and in samples with significant disorder. These results were obtained by time-resolved nanophotoluminescence with 5 ps and 250 nm temporal and spatial resolution, respectively 关键词: excitons;II-VI semiconductors;phonon spectra;photoluminescence;semiconductor quantum wells;time resolved spectra;wave functions;zinc compounds;ultrafast breathinglike oscillation;exciton density;ZnSe quantum wells;spatial density profile;low-density exciton ensemble;first acoustic phonon;quasiballistic transport phase;scattering;excitonic wave function;coherence length;coherence time;excitonic transport;Monte Carlo simulations;lattice temperature;phonon absorption;disorder;time-resolved nanophotoluminescence;temporal resolution;spatial resolution;30 ps;ZnSe