Regensburg 2004 – scientific programme

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HL: Halbleiterphysik

HL 44: Poster II

HL 44.39: Poster

Thursday, March 11, 2004, 16:30–19:00, Poster A

Damping of Rabi oscillations in quantum dots due to carrier-phonon resonance — •Paweł Machnikowski, Vollrath Martin Axt, and Tilmann Kuhn — Institut für Festkörpertheorie, Universität Münster, Wilhelm-Klemm-Str. 10, 48149 Münster

We describe the dynamics of an exciton in an InAs/GaAs quantum dot under coherent optical excitation in the presence of coupling to lattice modes (acoustical and optical phonons). We show that the interaction between the confined carriers and the surrounding lattice under external driving of the carrier dynamics has a dynamical, resonant character. By solving the non-Markovian Master equation for the reduced density matrix of the carrier subsystem (in Born approximation, i.e. including one-phonon effects) we find the dot occupation upon excitation with a Gaussian pulse of fixed duration and varying amplitude. Coupling to lattice modes reduces the amplitude of these oscillations, the effect being small for short pulses and increasing for longer pulses. However, for still longer pulses, the quality of Rabi oscillation again improves. We show that only for long pulses a truly coherent control is realized, while short pulses drive the system through unstable (decohering) states, corresponding to non-equilibrium lattice state. We show that the damping of Rabi oscillations is due to a resonance between the induced carrier dynamics and the lattice modes.