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

• Applicants: Professor Dr. Gerd Czycholl; Professor Dr. Frank Jahnke
• Subject Area: Theoretical Condensed Matter Physics
• Term: from 2014 to 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 257838310

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.

• DFG Programme: Research Grants