Dresden 2011 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 85: Poster Session II
HL 85.33: Poster
Donnerstag, 17. März 2011, 18:00–21:00, P4
Squeezing of lattice displacement due to anharmonic decay of phonons in a semiconductor quantum dot — •Jonas Daniels1, 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
Squeezed states of light have attracted large interest due to a possible reduction in the noise limit of quantum measurements. A standard tool for the generation of squeezed light is parametric down conversion. In many semiconductor materials similar processes exist for phonons, e.g., the anharmonic decay of a longitudinal optic (LO) phonon into a pair of longitudinal acoustic (LA) phonons. Here we study theoretically the fluctuation properties of the lattice displacement and the lattice momentum connected to the LA phonons generated by this decay process. We consider the impulsive creation of an exciton in a semiconductor quantum dot structure. This is accompanied by the generation of LO phonons, which then may decay into entangled pairs of LA phonons. We perform quantum kinetic calculations to analyze the lattice fluctuations related to these LA phonons. We find that a squeezing of the lattice fluctuations occurs, which is confined within the dot area, although LA phonon wave packets travel out of the dot. The strength and the localization of the squeezing effect can be manipulated by an external electric field which strongly affects the coupling of the exciton to the LO phonons and thus the generation process of the LO phonons.