IMX Colloquium - Ultrafast Electron Microscopy and Free-Electron Quantum Optics

Providing the most detailed views of atomic-scale structure and composition, Transmission Electron Microscopy (TEM) serves as an indispensable tool for structural biology and materials science. The combination of electron microscopy with pulsed electrical or optical stimuli allows for the study of transient phenomena, involving magnetization dynamics, strain evolution and structural phase transformations. Ultrafast transmission electron microscopy (UTEM) is a pump-probe technique, which tracks non-equilibrium processes with simultaneous femtosecond temporal and nanometer to atomic-scale spatial resolutions.
This talk will introduce UTEM based on laser-triggered field emitters, and will provide application examples, such as the real-space imaging of structural phase transitions [1] and the coherent mapping of optical fields [2]. Beyond time-resolved imaging, light-coupled TEMs also serve as testbeds for free-electron quantum physics, facilitating the study of electron-electron [3,4] as well as electron-photon [5] correlations and entanglements [6].
References:
[1] "Ultrafast nanoimaging of the order parameter in a structural phase transition”, Th. Danz, T. Domröse, C. Ropers, Science 371, 6527 (2021)
[2] J. H. Gaida et al., “Attosecond electron microscopy by free-electron homodyne detection”, Nature Photonics 18, 509–515 (2024).
[3] R. Haindl et al., “Coulomb-correlated electron number states in a transmission electron microscope beam”, Nature Physics 19, 1410–1417 (2023).
[4] R. Haindl et al., “Femtosecond and Attosecond Phase-Space Correlations in Few-Particle Photoelectron Pulses”, Phys. Rev. Lett. 135, 165002 (2025).
[5] A. Arend et al., “Electrons herald non-classical light“, Nature Physics 21, 1855–1862 (2025).
[6] J.-W. Henke et al., “Observation of quantum entanglement between free electrons and photons”, arXiv:2504.13047(2025).

Bio: Claus Ropers studied physics in Göttingen and at the University of California, Berkeley. He completed his PhD at the Max Born Institute and the Humboldt University Berlin in 2007, and became assistant professor in back in Göttingen in 2008.  Since 2020, he has been Director at the Max Planck Institute for Multidisciplinary Sciences. His interests lie in the development of ultrafast electron microscopy and the study of nanoscale light-matter interactions and free-electron quantum optics.