Nano-femto-control of cooperative dynamics in van der Waals quantum materials
Technologically relevant processes in semiconductors take place at lightning speed and on the tiniest length scales. For a comprehensive understanding of novel van der Waals materials, it is crucial to track the dynamics of electrons and collective excitations with ultra-high-resolution slow-motion movies. We are therefore developing new methods to combine a spatial resolution of a few nanometers with ultrafast time resolution in the range of only a few femtoseconds.
| Place of research | University Regensburg |
| Association | Elite Graduate Program “Physics with integrated Doctorate Program” |
| Project duration | 2024 to 2030 |
| Group leader | Dr. Fabian Mooshammer Contact the group leader |
| Further information | Website NanoFemtoCoop |
Tracking dynamics in solids in space and time
Modern microscopes can readily take still images of the nanoworld. However, technologically relevant processes, such as the movement of electrons in a solar cell, take place not only on length scales of a few nanometers (billionths of a meter), but also on ultrafast time scales of just a few femtoseconds (millionths of a billionth of a second). In order to exploit the full potential of novel materials for more efficient components and completely new applications, the development of new microscopy methods that can record videos of the nanoworld in motion is therefore crucial.
The Junior Research Group is working on this highly topical subject, which is also a central goal of the “Regensburg Center for Ultrafast Nanoscopy” (RUN). There, the group has ideal starting conditions with brand new laboratories, world-class instrumentation, and an interdisciplinary research environment.
The focus of the Junior Research Group is on the combination of ultrashort flashes of light with scanning probe microscopy. The laser pulses are coupled to sharp metallic tips, which concentrates the light like a lightning rod. With such a source of nano-light, optical properties and elementary excitations can then be measured with a spatial resolution that is many orders of magnitude beyond the diffraction limit.
Novel van der Waals crystals consist of individual layers that are only a few atoms thick. The best-known representative is graphene - individual layers of carbon atoms that are loosely stacked on top of each other, for example in the lead of a pencil. Closely related to this are the semiconducting transition metal dichalcogenides. Compared to conventional semiconductors used in cell phones or computers, the atomically thin representatives have additional unique properties for applications in optoelectronics.
Furthermore, electrons in van der Waals heterostructures behave completely differently under certain circumstances than is known from conventional semiconductors. The electrons not only move freely through the two-dimensional layer, but can also arrange themselves regularly, similar to the crystal lattice of atoms itself. Each electron is then so strongly repelled by its neighbors that it is stuck in its place.
An International Junior Research Group offers ideal conditions for pursuing your own research ideas, also in comparison with other national or Europe-wide funding programs.
Dr. Fabian Mooshammer
Super slow-motion movies of the behavior of electrons with different numbers of interaction partners would provide important insights into these extraordinary quantum phases, which hold immediate relevance for future quantum technologies. On the one hand, the properties of solids can be “simulated” and compared with current theoretical models. In the experiment, such a high number of interacting particles could potentially be taken into account that even high-performance computers would reach their limits with comparable calculations. On the other hand, these periodic lattices could serve as sources for individual photons, which could be relevant for applications in quantum information.