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

半导体量子点目前正被用作活性材料，在新型光电子器件中有着广泛的应用。这包括从传统的半导体激光器、放大器和调制器到单光子和纠缠光子对的来源，这些都是量子信息技术的关键组件。强大的应用潜力和相对于现有活性材料的众多优势导致了该领域的高度实验和理论研究活动。在实际应用中，散射过程起着核心作用：它们在光学活跃的电子态中提供载流子，并决定光学跃迁的退相干。特定激发条件下的载流子散射效率为器件设置了固有的限制，例如发射的饱和、调制速率和工作温度区域。退相干的强度直接决定了发射线的宽度、相干性质、纠缠度等发射性质。以往描述半导体纳米结构中的散射过程和载流子关联的理论模型都是采用单粒子布居，或者基于一系列期望值的近似展开。然而，特别是在量子点中，三维载流子限制，以及相对较少的电子构型，使电子关联效应受到了更大的重视。这给目前使用的方法带来了新的视角，并质疑了它们在某些激发条件下的适用性。该项目的范围包括基于组态的描述量子点中的电荷载流子散射过程，其数值实现，以及理论和实验之间的直接合作，以评估结果并提供新的推动力。起始点是单粒子态，它与库仑相互作用一起导致多激子组态。用这些组态描述了相邻连续态载流子的散射过程，以及载流子与声子之间的相互作用。这项工作将汇集非平衡格林函数量子动力学模型和基于关联的量子光学效应描述的专业知识。

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.