Configuration-picture-description of carrier scattering in semiconductor quantum dots

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Semiconductor quantum dots are currently being used as active material for a multitude of applications in novel optoelectronic devices. This ranges from conventional semiconductor lasers, amplifiers, and modulators to sources of single photons and entangled photon pairs, which are key components for quantum information technologies. Strong application potential and numerous advantages over established active materials have led to high experimental and theoretical research activity in this field. For practical purposes, scattering processes play a central role: They provide carriers in the optically active electronic states and determine the decoherence of optical transitions. The efficiency of carrier scattering for particular excitation conditions sets intrinsic limitations for devices, such as saturation of the emission, modulation rates, and the operative temperature regime. The strength of decoherence directly determines the emission line widths, coherence properties, degrees of entanglement, and other emission properties.Previous theoretical models for the description of scattering processes and carrier correlations in semiconductor nanostructures have used single-particle populations, or they were based on the approximate expansion of a hierarchy of expectation values. Particularly in quantum dots, however, the three-dimensional carrier confinement, and the comparatively small number of electronic configurations, puts a much stronger emphasis on electronic correlation effects. This places currently used methods in a new light and questions their applicability under certain excitation conditions, as demonstrated in current publications.The scope of this project comprises a configuration-based description of charge carrier scattering processes in quantum dots, its numerical implementation, as well as a direct collaboration between theory and experiment to evaluate the results and provide new impulses. Starting point are the single-particle states that lead, in combination with the Coulomb interaction, to the multi-exciton configurations. Scattering processes with carriers in adjacent continuum states, as well as the interaction between carriers and phonons, are formulated in terms of these configurations. This undertaking will bring together expertise from non-equilibrium Green's function quantum-kinetic models and the correlation-based descriptions of quantum-optical effects.