Dresden 2009 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 48: Poster 2

HL 48.38: Poster

Donnerstag, 26. März 2009, 15:00–17:30, P2

Coherent LO phonons in optically excited double quantum wells — •Thomas Papenkort¹, Tilmann Kuhn¹, and Vollrath Martin Axt² — ¹Institut für Festkörpertheorie, Universität Münster, Wilhelm-Klemm-Str. 10, 48149 Münster — ²Institut für Theoretische Physik III, Universität Bayreuth, 95440 Bayreuth

In a double quantum well with a sufficiently thin barrier between the wells the two wells couple, i.e. the subbands are no longer localized in one of the wells but extend over both. By optically exciting such a double well under the influence of a static electric field an electron density can be obtained which is localized in one of the two wells. Because of tunneling the electrons oscillate between the two wells with the frequency of the subband splitting. This causes an oscillating polarization which couples strongly to a polar lattice, thereby creating coherent LO phonons.

We present numerical calculations of this efficient phonon generation process in an AlGaAs-GaAs double quantum well. Using a quantum kinetic approach we calculate both the dynamics of the electronic subsystem driven by a semi-classical laser field and of the phonons created via the Fröhlich interaction. We study the coherent amplitude and the fluctuations of the generated phonon states. They depend on the subband structure, which is defined by the dimensions of the double quantum well and the strength of the electric field, as well as on the exact excitation conditions.