@article{HartmannZimmermannStolz1990, author = {Hartmann, Michael and Zimmermann, R. and Stolz, Heinrich}, title = {Kinetics of Screening in Optically Excited Semiconductors}, series = {Physica Status Solidi (B)}, volume = {159}, journal = {Physica Status Solidi (B)}, number = {1}, url = {http://nbn-resolving.de/urn:nbn:de:0298-opus4-6028}, pages = {35 -- 42}, year = {1990}, abstract = {Kinetic equations for the density correlation and density-density response function are derived. Solving these equations numerically and comparing its solution with the adiabatic approximation the change in the transmitted spectrum of a single electronic transition is calculated where a red-shift can be observed. Es werden kinetische Gleichungen f{\"u}r die Di Dichtekorrelationsfunktion und die Dichte-Dichte-Responsefunktion abgeleitet. Die numerische L{\"o}sung dieser Gleichungen wird mit der adiabatischen Approximation verglichen. Die Berechnung der {\"A}nderung im Transmissionsspektrum f{\"u}r einen einzelnen elektronischen {\"U}bergang ergibt eine Rotverschiebung.}, language = {en} } @article{ZimmermannHartmann1990, author = {Zimmermann, R. and Hartmann, Michael}, title = {Theory of the dynamical stark effect of excitons in CdS}, series = {Journal of Crystal Growth}, volume = {101}, journal = {Journal of Crystal Growth}, number = {1-4}, pages = {341 -- 345}, year = {1990}, abstract = {The dynamical Stark effect of excitons in CdS bulk crystals has been measured recently using differential transmission spectroscopy (DTS). A general DTS formula is derived taking into account exciton-exciton interaction. A perculiar influence of the pump and test polarization on its magnitude is predicted. Concerning the dephasing (transverse relaxation), coupling to optical phonons is treated on a microscopic level. A density-matrix approach leads to the imaginary part of the exciton-phonon self energy. Its strong frequency dependence which shows up as a non-Markoff relaxation strongly suppresses the relaxation for the pump pulse at large detuning. A more sophisticated approach using the non-equilibrium Green function gives deeper insight into the underlying scattering processes.}, language = {en} } @article{ZimmermannHartmann1988, author = {Zimmermann, R. and Hartmann, Michael}, title = {Resonant and Off-Resonant Light-Matter Interaction in Semiconductors Kinetics and Transients}, series = {Physica Status Solidi (B)}, volume = {150}, journal = {Physica Status Solidi (B)}, number = {2}, url = {http://nbn-resolving.de/urn:nbn:de:0298-opus4-6048}, pages = {365 -- 378}, year = {1988}, abstract = {Kinetic problems for off-resonance excitation (dynamical Stark effect) and resonant excitation (laser-induced gaps) are studied. Within the Hartree-Fock theory, Stark shift and bleaching of the exciton line are evaluated. The influence of photon statistics on light-induced gaps is investigated. Open questions concerning the transient response are clarified. Es werden kinetische Probleme f{\"u}r nichtresonante Anregung (dynamischer Stark-Effekt) und resonante Anregung (laserinduzierte L{\"u}cken) betrachtet. Im Rahmen der Hartree-Fock-Theorie werden Stark-Verschiebung und Oszillatorst{\"a}rken{\"a}nderung f{\"u}r die Exzitonlinie berechnet. Der Einfluß der Photon-Statistik auf die lichtinduzierten L{\"u}cken wird untersucht. Einige offene Fragen des Kurzzeit-Response werden gekl{\"a}rt.}, language = {en} } @article{HartmannZimmermannStolz1988, author = {Hartmann, Michael and Zimmermann, R. and Stolz, Heinrich}, title = {Carrier Kinetics in a Semiconductor with Light-Induced Gaps}, series = {Physica Status Solidi (B)}, volume = {146}, journal = {Physica Status Solidi (B)}, number = {1}, pages = {357 -- 369}, year = {1988}, abstract = {Due to the influence of a strong electromagnetic field an induced gap is expected to occur in the band structure of a semiconductor. In this paper the influence of the damping by electron-phonon collisions and by recombination on the new band structure is investigated. Taking into account damping kinetic equations for the electrons are derived and discussed with the help of calculations. Unter dem Einfluß eines starken elektromagnetischen Feldes kommt es in der Bandstruktur eines Halbleiters zur Ausbildung eines Zusatzgaps. In dieser Arbeit wird der Einfluß der D{\"a}mpfung durch Elektron-Phononst{\"o}ße und Rekombination auf die neue Bandstruktur untersucht. Weiterhin werden kinetische Gleichungen unter Ber{\"u}cksichtigung der D{\"a}mpfung abgeleitet und an Hand von numerischen Berechnungen diskutiert.}, language = {en} }