DOI: 10.5281/zenodo.17975297
title: Femtosecond concerted rotation of molecules on a 2D material interface

description: This dataset was measured using a momentum microscopeby integrating four modalities of time-resolved photoelectron spectroscopy: Interfaces between molecules and 2D materials exhibit energy-driven functionalities, wherein charge transfer directs molecular motion. Unlike equilibrium systems, where molecular assemblies settle into static configurations, continuous energy input can drive transient, collective molecular rearrangements. Here, we reveal ultrafast spectroscopic fingerprints of a collective rotational response of molecules on a 2D material following photoexcitation. Our results suggest that photoinduced charge transfer reshapes the interfacial energy potential, giving rise to macroscopic, unidirectional molecular rotation and the formation of a homochiral molecular arrangement. Using a multiplexed ultrafast photoemission spectroscopy approach, we simultaneously track, electronic states, atomic positions, and orbital wavefunctions with femtosecond and sub-Ångström resolution. Multimodal valence and core electron emission analysis disentangles the intertwined electronic-structural dynamics of the molecule and the 2D material, revealing the dynamic modulation of charge distribution and intermolecular forces that drive collective molecular motion. Our findings open a pathway for designing energy-driven molecular systems with tunable interfacial dynamics, with potential applications in chiral engineering and active matter systems.
description: Acknowledgements: The authors would like to thank Holger Meyer and Sven Gieschen for instrumentation support, and Bernhard Mahlmeister for his contribution to Fig. 1.

Funding: We thank DESY (Hamburg, Germany), a member of the Helmholtz Association HGF, for the provision of experimental facilities. Parts of this research were carried out at FLASH using beamline PG2. Beamtime was allocated for proposal 20190734. The photoemission spectroscopy instrument at beamline P04 was partially funded by the German Federal Ministry of Education and Research (BMBF) under the ErUM program (project 05K22FK2). KB, CM and FR acknowledge financial support of the Deutsche Forschungsgemeinschaft (DFG) through the Würzburg-Dresden Cluster of Excellence ctd.qmat (EXC 2147, project id 390858490). MR and DP-G acknowledge the funding from the Volkswagen Foundation, project ID 96237. KC acknowledge funding from the Cluster of Excellence 'CUI: Advanced Imaging of Matter' of the Deutsche Forschungsgemeinschaft (DFG) - EXC 2056 - project ID 390715994. DP-GMN acknowledges the student dispatch program by the Japan Student Services Organization (JASSO). MN, MH and KN thank the Supercomputer Center, the Institute for Solid State Physics and the University of Tokyo for the use of their facilities and acknowledge financial support from the Grants-in-Aid for Scientific Research (C) (No. 20K05643) from Japan Society for the Promotion of Science and the Initiative for Realizing Diversity in the Research Environment of Chiba University. NW, MH, DK, SM and KR acknowledge financial support from the DFG (SFB 925, project ID 170620586).
description: Data availability.
The experimental data are provided in IgorPro formats (.ibw and .pxp), together with results from calculations. Files fig1b to fig1f4 correspond to the data shown in Fig. 1; files fig2a to fig2e correspond to Fig. 2;files fig3a to fig3cb correspond to Fig. 3;files figS1 to figS25 contain the data for the Supplementary Materials.