Real-time quantum simulations of ultrafast exciton dynamics with atomic resolution

• Applicant: Dr. Jan Wilhelm
• Subject Area: Theoretical Condensed Matter Physics
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 503985532

A recent breakthrough in ultrafast scanning probe microscopy made it possible for the first time to experimentally visualize electron dynamics on the femtosecond time and atomic length scale. This technique enables the experimental monitoring of the time evolution of chemical reactions or excited electronic states, such as excitons. At present there is no computational method that would allow for a comparable spatio-temporal resolution with quantitative predictability. I here propose to implement a theoretical machinery with the potential to close this gap. My methodology will provide the insights needed for a detailed understanding of the ongoing experiments and the fundamental processes they display, that otherwise are very hard if not impossible to achieve. The proposal is to advance the GW-method, which is an extremely successful tool for electronic structure calculations, so it also becomes applicable in the time domain for the experimentally relevant system sizes. Simulations of ultrafast electron dynamics will become feasible with atomic resolution for realistic materials. Building on my previous work and experience, I expect to be able to facilitate time-dependent GW (TDGW) simulations with an unprecedented number of hundreds of atoms. Such large-scale TDGW computations are crucial for simulating the electron dynamics at defects and interfaces, which are relevant, e.g., to understand loss mechanisms at defects in solar cells. Further, to validate the standard approximation scheme, I will extend the ab-initio TDGW formalism beyond the adiabatic scheme to enable benchmarks. Applications of the newly implemented TDGW will focus on exciton dynamics in thin-film transition-metal dichalcogenides. Of special interest is exciton trapping at defects, e. g. because they have a technological potential as exciton binding centers for single-photon emitters – building blocks for future quantum information devices. As a candidate structure for ordered arrays of such devices, I also will analyze the exciton propagation in moiré structures. These studies will be performed in close collaboration with my experimental partners, who will monitor the exciton dynamics with atomic resolution using state-of-the-art ultrafast scanning-probe microscopy. Our joint experiment-theory collaboration will ultimately shed light on the fundamental mechanisms of exciton dynamics on the intrinsic time and length scales.

• DFG Programme: Independent Junior Research Groups
• International Connection: Switzerland
• Cooperation Partner: Professor Dr. Jürg Hutter