Hybrid quantum opto-electronic devices based on excitons in van der Waals heterostructures

• Applicant: Dr. Nadine Leisgang
• Subject Area: Experimental Condensed Matter Physics
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 553875273

Motivation: The pursuit of scalable quantum technologies has led to an ever-increasing demand for better control of quantum properties of materials. Two-dimensional (2D) materials represent a promising platform for engineering quantum systems. These materials can be metallic, semiconducting, or insulating, and can possess a whole variety of optical and electronic properties. By stacking layers of different 2D materials on top of each other - through van der Waals engineering - new hybrid structures can be created in a highly flexible and controlled way. Scientific strategy and objectives: My research combines nano-fabrication, (magneto-)optics and electrical transport with the aim to create, control and sense hybrid quantum systems based on 2D materials. The specific goal is to engineer quantum states in 2D semiconducting devices and to employ the strong interaction between particles in these systems in order to manipulate and explore exotic quantum phenomena. Of particular interest are atomically-thin transition metal dichalcogenides (TMDs) as they strongly interact with light. Their optical properties are governed by excitons - electrons and holes bound by Coulomb attraction - that remain stable up to room-temperature. We will focus on the realization of complex opto-electronic devices based on excitons in van der Waals heterostructures. Building upon these well-assembled structures, we will investigate charge transfer dynamics and interlayer coupling phenomena in both bilayer and multilayer systems. Understanding these processes will be crucial for manipulating the electronic and optical properties across different layers, as well as enhancing and controlling the interactions between charge carriers within these systems. Based on this work, we will then focus on realizing quantum light-emitting diodes using monolayers of p-type and n-type TMDs. Our goal is to gain full control of the new quantum states through dielectric engineering and electrical gating, and to investigate the strong correlation between electrons and holes and the transport of excitons in the system. Relevance and impact: Semiconducting TMDs provide many technological advantages. While being atomically-flat without any dangling bonds, these optically-active layers can be integrated with a wide range of 2D materials with different properties. In addition, these systems are highly tunable through many experimental parameters, such as carrier density, external electric and magnetic fields, layer composition, relative twist angles, dielectric environment, and so on. The ability to engineer and control the properties of the thin semiconductors makes these systems a versatile platform for rich exciton and electron physics and unique opto-electronic applications based on light emission, detection and manipulation.

• DFG Programme: Emmy Noether Independent Junior Research Groups
• International Connection: Switzerland
• Major Instrumentation: Closed-cycle cryostat ; Spectrometer (incl. Software)
• Instrumentation Group: 5890 Sonstige Photodetektoren (außer 580-586) ; 8550 Spezielle Kryostaten (für tiefste Temperaturen)
• Cooperation Partner: Professor Dr. Richard Warburton