Berlin 2012 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 43: Poster Session: Quantum Dots and Wires - Preparation and Characterization / Devices (incl. Laser) / Ultrafast Phenomena
HL 43.26: Poster
Dienstag, 27. März 2012, 09:30–12:30, Poster D
Optical excitation conditions for generating squeezed phonon states in a quantum dot — •Daniel Wigger1, Doris E. Reiter1, Vollrath Martin Axt2, and Tilmann Kuhn1 — 1Institut für Festkörpertheorie, Westfälische Wilhelms-Universität Münster, Wilhelm-Klemm-Str. 10, 48149 Münster — 2Theoretische Physik III, Universität Bayreuth, 95440 Bayreuth
We study theoretically squeezing properties of phonons generated after optical excitation of a semiconductor quantum dot (QD). We model the QD in the strong confinement limit as a two level system coupled by the Fröhlich interaction to longitudinal optical (LO) phonons. An ultrashort laser pulse creates an exciton in the QD, which leads to a shift of the equilibrium position of the lattice ions. Thus lattice vibrations, i.e. phonons, are created. For an excitation with two pulses we find that Schrödinger cat states, i.e. superpositions of coherent states, build up. Depending on the time delay and relative phase between the pulses and on the coupling strength the fluctuation properties of theses states can fall below their vacuum limit, i.e. squeezing occurs [1]. By using the Wigner function we can illustratively analyze the influence of the material and excitation parameters on the fluctuation properties.
[1] Sauer et el., PRL 105, 157401 (2010)