Regensburg 2004 – wissenschaftliches Programm

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HL: Halbleiterphysik

HL 28: Optische Eigenschaften

HL 28.1: Vortrag

Mittwoch, 10. März 2004, 15:15–15:30, H17

Exciton-Phonon Dynamics in Disordered Quantum Wells beyond the Markov Approximation — •Gianandrea Mannarini and Roland Zimmermann — Institut für Physik der Humboldt-Universität zu Berlin, Newtonstr.15, 12489 Berlin, Germany

Exciton motion in semiconductors is coupled to the thermal bath of phonons due to carrier-lattice interactions. Within the density-matrix formalism, a hierarchy of equations of motion is derived which contains memory (non-Markovian) effects. Assuming very short collision times, the exciton-phonon interaction can be described in terms of scattering rates. This Markov approximation could explain quantitatively the spectral properties of the excitonic secondary emission [1]. However, in ultrafast experiments a more complex dynamics is expected. Actually, a non -Markovian dynamics was predicted and observed for the electron-LO phonon system [2]. Here, we adopt a non-Markovian treatement for localized excitons in single quantum wells coupled to acoustical phonons via deformation potential interaction. The equations of motion with memory for the exciton polarization and density matrix are integrated and the effect on the time-resolved dynamics of the secondary emission and the speckle pattern is calculated. [1] G. Mannarini, R. Zimmermann, G. Kocherscheidt, and W. Langbein, phys. stat. sol. (b), 238, 494 (2003). [2] C. Fürst, A. Leitenstorfer, A. Laubereau, and R. Zimmermann, Phys. Rev. Lett. 78, 3733 (1997).