Dresden 2006 – wissenschaftliches Programm

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HL: Halbleiterphysik

HL 50: Poster II

HL 50.86: Poster

Donnerstag, 30. März 2006, 16:30–19:00, P3

The role of non-equilibrium phonons for the optically induced dynamics in quantum dots — •Annette Krügel, Vollrath Martin Axt, and Tilmann Kuhn — Institut für Festkörpertheorie, Westfälische Wilhelms-Universität, 48149 Münster, Deutschland

For GaAs type quantum dots it has been shown that pure dephasing due to the coupling to longitudinal acoustic (LA) phonons gives a major contribution to the initial dephasing on picosecond time scales. For high density excitation also the phonon system is driven out of its equilibrium state and coherent phonon amplitudes and non-equilibrium phonon coherences and occupations act back on the carrier system. We study the exciton dynamics in a quantum dot coupled to LA-phonons. The carriers are excited by Gaussian laser pulses of arbitrary duration. For the electron-phonon interaction we concentrate on pure dephasing processes described by the independent boson model. Numerical results are obtained by using a correlation expansion within the density matrix formalism. We account for all single and double assisted density matrices as well as for the coherent phonon amplitudes and non-equilibrium phonon occupations and correlations. A pronounced influence of these non-equilibrium phonons on the carrier dynamics is observed. We find that especially for low temperatures and longer pulses of several picoseconds non-equilibrium phonons play an important role and cannot be neglected.