Structural Dynamics and Optical Properties
In a superficial description of optical and electronic properties, the underlying lattice is often viewed as the stage on which the electronic dynamics plays out: providing the static foundation for the electronic properties to be defined. On the other hand, the lattice dynamics define the thermal properties of a solid. Obviously, the systems are coupled, leading to basic phenomena such as resistivity heating in conductors.
We are interested how dynamical changes of the crystal structure determine the optical properties of materials, on the time-scale of lattice dynamics (< 1 ps) as well as in the stationary state. We combine our expertise in organic semiconductors and plasmonic nano structures with state-of-the-art pump-probe and spectroscopic techniques as well as computational quantum chemistry to investigate exciton-phonon coupling in modern materials keeping their opto-electronic applications in mind.
Current Work
Structural distortions in organic semiconductors
[1] Excimer formation in zinc-phthalocyanine reveald by ultrafast electron diffraction
Hammer S., Brit T. L., Kremeyer L., Rödel M., Cai D., Pflaum J. Siwick B. J. (2024). PNAS [DOI]
[2] Spectroscopic analysis of vibrational coupling in multi-molecular excited states
Hammer S., Linderl T., Tvingstedt K., Brütting W., Pflaum J. (2023). Mater. Horiz. [DOI]
Towards highly efficient plasmonics
[3] Ag100-xAux alloy films: An approach to fix silver for durable. low-loss plasmonics
Ewald B., Siebigs L., Zhang V., Graf J., Tiwari A., Rödel M., Hammer S., Stepanenko V., Würthner F., Gompf B., Hecht B., Pflaum J. (2025). ACS Photonics. [DOI]
Experimental and Computational methods:
- Femtosecond Transient NIR-Reflectivty
- µ-Photoluminescence and Photoluminescence Excitation Spectroscopy from 4 K to 400 K.
- Ultra-Microtomy for sub-100 nm single crystal specimen
- Uv-Vis transmission microscopy
- Density Functional Theory (DFT) to predict material properties
- Ultrafast Electron Diffraction (external)
- Femtosecond Transient Absorption Spectroscopy (external)
If you are interested in a specific topic of our research or are looking for a bachelor or master thesis Dr. Sebastian Hammer.
