FEMTOSECOND RELAXATION KINETICS OF HIGHLY EXCITED ELECTRONIC WAVE-PACKETS IN SEMICONDUCTORS

We present a theoretical study of the ultrafast decoherence process of an electronic wave packet in a semiconductor quantum well exposed to a strong magnetic field. A conduction-band electron is excited into a coherent superposition of Landau levels by an ultrashort laser pulse. Subsequently, the coupling to a continuum of optical phonons induces a rapid decoherence. It is shown that the time evolution of the-electro n Wigner function and the distribution profile of the emitted phonons are sensitive; probes of the decoherence process. Various non-Markovia n and Markovian kinetic theories are tested for their ability tb descr ibe the relaxation of a wave packet. [S0163-1829(98)12819-9].