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O: Fachverband Oberflächenphysik
O 14: Ultrafast electron dynamics at surface and interfaces I
O 14.3: Vortrag
Montag, 9. März 2026, 15:45–16:00, TRE/MATH
Multi-mode momentum microscopy for studying light-induced metastable states — •Junde Liu1, Bent van Wingerden1, Hashima Marukara1, Paul Werner1, Daniel Steil1, G. S. Matthijs Jansen1, Wiebke Bennecke1, Jan Philipp Bange1, Olena Tkach2, Gerd Schönhense2, and Stefan Mathias1 — 1Georg-August-Universität Göttingen, Germany — 2Johannes Gutenberg-Universität Mainz, Germany
Light-induced ultrafast phase transitions characterized by domain competition involving interlayer ordering, chirality, and topological defects are attracting growing interest [1]. This calls for time-resolved momentum microscopy, which offers simultaneous spatiotemporal resolution and direct access to band structures [2]. However, conventional high-field setups near the sample are prone to field-emission and space-charge effects, particularly in the case of cleaved crystal surfaces.
Here, using cleaved bulk TaS2 as an exemplary system, we employ a momentum microscope with a newly designed lens system [3] that minimizes the electric field at the sample in the gap-lens mode to suppress field emission, or applies a retarding field in the repeller mode to remove slow electrons and thereby mitigates space-charge effects. This development paves the way to study cleaved crystals and enables dark-field imaging capabilities of domain-resolved electronic structure, nonequilibrium pathways, and the microscopic mechanisms of light-driven phase transitions. [1] Liu et al., arxiv:2405.02831 (2024); [2] Reutzel, Jansen, Mathias, Adv. in Phys. X 9, 2378722 (2024); [3] Tkach & Schönhense, Ultramicroscopy 276, 114167 (2025).
Keywords: Momentum microscopy; Multiple lens mode; Photo-induced phase transitions