Many-body theory of optical properties for semiconductor nanostructures based on atomistic tight-binding models

该项目研究了三种不同类型的光学活性纳米结构（自组织量子点、纳米晶体、单层二硫化钼），它们的共同之处在于，光学性质只能在结构性质和多体效应的相互作用中被理解。这些纳米结构涵盖了广泛的应用，包括改进的传统光电器件和非经典光源（量子点），更高效的太阳能电池和荧光生物标签（纳米晶体），以及基于新材料的晶体管，发光器和探测器（单层二硫化钼）。该项目旨在将电子性质的原子模型与光学性质的多体模型联系起来，这两种模型由于其复杂性而经常被独立考虑。为此目的，将把在这些领域具有广泛经验的两个小组的专门知识结合起来。五个不同的子项目将用于建立这种联系。斯图加特的Michler教授小组基于应变工程制造了新的InGaAs量子点结构，该结构允许将发射波长转移到1.3µm至1.5µm的范围内。这对于基于光纤的应用来说是特别有趣的。与实验发展直接相关，我们的理论研究将澄清应用方法的潜在范围和局限性，并有助于样本设计。其他子项目将研究高激发条件下实际量子点系统的增益饱和和增益减小，非极性氮化物量子点系统的光学特性，以及无序III-V和ii - vi纳米晶体。研究的核心部分将集中在单层二硫化钼的光学性质上。这种非凡的材料具有与石墨烯相似的机械和电子特性，同时表现出直接光学带隙。关于光发射效率和光电子应用潜力的开放性问题将在超越基态性质的形式中得到解决。

The project addresses three different types of optically active nanostructures (self-organized quantum dots, nanocrystals, monolayer molybdenum disulfide) which have in common that the optical properties can only be understood in the interplay of structural properties and many-body effects. These nanostructures cover a broad range of applications including improved conventional optoelectronic devices and nonclassical light sources (quantum dots), more efficient solar cells and fluorescent biological labels (nanocrystals), as well as new-material-based transistors, light emitters and detectors (monolayer molybdenum disulfide). This project aims at the connection of atomistic models for electronic properties and many-body models for optical properties, which are frequently considered independently due to their complexity. For this purpose, the expertise of two groups, having extended experience in these fields, will be combined. Five distinct sub-projects will be used to establish this connection. The group of Prof. Michler in Stuttgart fabricates new InGaAs quantum-dot structures based on strain engineering, which allow shifting the emission wavelength into the range of 1.3 µm to 1.5 µm. This is of particular interest for fiber-based applications. In direct connection with the experimental developments, our theoretical investigations will clarify the potential range and limitations of the applied methods as well as aid the sample design. Other sub-projects will address gain saturation and gain reduction of realistic quantum-dot systems under high excitation conditions, optical properties of non-polar Nitride quantum-dot systems, as well as disordered III-V and II-VI-nanocrystals. A central part of the investigations will focus on the optical properties of monolayer molybdenum disulfide.This extraordinary material has mechanical and electronic properties similar to graphene while exhibiting a direct optical bandgap. Open questions regarding the light emission efficiency and the potential for optoelectronic applications will be addressed within a formalism that goes beyond ground-state properties.