Time-resolved low energy photoelectron diffraction for the study of surface structural dynamics with sub-100 fs temporal resolution

• Applicant: Professor Dr. Michael Bauer
• Subject Area: Experimental Condensed Matter Physics
• Term: since 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 433458487

In the first funding period of this project, the central goals of the application were achieved: a clear photoelectron diffraction signal due to the long-range order of the adsorbate layer on the test system SnPc adsorbed on graphite could be identified. Furthermore, a time resolution of 100 femtoseconds could be demonstrated in time-resolved photoelectron diffraction experiments. In addition, heating of the adsorbate layer on picosecond time scales was observed in the transient diffraction signal. In parallel, the electron dynamics in the substrate could be followed in the same experiment. Finally, a high harmonic source has been successfully implemented in the time-resolved photoemission experiment and will significantly expand the possibilities of time-resolved photoelectron diffraction in the future. Based on these results, the potential of the technique of time-resolved photoelectron diffraction with low-energy electrons (LEPD) for investigations of the structural dynamics of adsorbates will be exploited in the upcoming funding period. The focus will be on studies of competing energy transfer processes during light-driven excitations of adsorbate-surface systems and on light-induced structural phase transitions within ordered adsorbate layers. Furthermore, the potential of momentum- and dark-field photoelectron microscopy for time-resolved LEPD experiments will be systematically explored. We expect the results to provide new insights into fundamental steps in the context of adsorbate-surfaces and adsorbate-adsorbate interaction processes. In addition, these experiments will further establish the new technique of time-resolved photoelectron diffraction with low-energy electrons.

• DFG Programme: Research Grants