Cooperative Atomic Motion in Solids probed by Femtosecond Transmission Electron Diffraction
Prof. Dr. Jure Demsar (Institut für Physik)

In numerous solids exhibiting broken symmetry ground states, changes in electronic (spin) structure are accompanied by structural changes. Here, we demonstrate an ultrafast transmission electron diffraction apparatus, where relative changes in the diffraction pattern of less than 1% can be studied with sub-picosecond time-resolution. Using a prototype two-dimensional charge density wave (CDW) system 1T-TaS2 as an example, we demonstrate that such studies provide direct access to the ultrafast dynamics of the CDW order parameter, and enable tracking photo-induced transformations between different macroscopically ordered phases.