Berlin 2008 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 42: Optical Properties of Quantum dots: Theory and Simulation

HL 42.10: Talk

Thursday, February 28, 2008, 12:15–12:30, EW 201

The impact of travelling phonon wave packets on quantum dot spectra — •Jan Huneke¹, Vollrath Martin Axt², and Tilmann Kuhn¹ — ¹Institut für Festkörpertheorie , WWU Münster, Wilhelm-Klemm-Str.10,48149 Münster — ²Institut für Theoretische Physik III, Universität Bayreuth, 95440 Bayreuth

The influence of phonon wave packets travelling across a semiconductor quantum dot on the optical spectra of the lowest quantum dot transition is analysed. Two situations are compared: (i) a phonon wave packet is generated by the optical excitation of a single quantum dot near a surface, which after reflection at the surface reenters the quantum dot; (ii) a phonon wave packet is generated by the excitation of a nearby second dot and then travels across the quantum dot. The analysis accounts for pure dephasing interactions between electronic and phononic degrees of freedom in quantum dot systems driven by ultrafast laser pulses. For this situation a generating function formalism provides exact analytical results. We find that although the displacement fields crossing the dot are almost identical in these two situations, the real time responses as well as the corresponding spectra exhibit qualitative differences and thus allow for a discrimination of phonon wave packets from different origins. By looking at the analytical results it is possible to trace back the physical origin of the differences in the above considered spectra to the fact that the phonons that cross the dot travel in different quantum mechanical subspaces namely: reflected phonon wave packets propagate in the single pair subspace while wave packets generated by a second dot travel in the two-pair manifold.