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O: Fachverband Oberflächenphysik
O 119: Non-Equilibrium Daynamics in Light-Driven Materials: Theory Meets Experiment
O 119.3: Talk
Friday, March 16, 2018, 12:00–12:15, MA 141
Hot phason dynamics in 1T-TaS2 probed by ultrafast LEED — •Theo Diekmann1, Gerrit Horstmann1, Simon Vogelgesang1, Gero Storeck1, Kai Rossnagel2, and Claus Ropers1 — 14th Physical Institute - Solids and Nanostructures, University of Göttingen, Friedrich-Hund-Platz 1, Germany — 2Institute for Experimental and Applied Physics, University of Kiel, Germany
We recently developed an ultrafast low-energy electron diffraction (ULEED) setup for the time-resolved study of structural dynamics. To implement this approach in a backscattering geometry, a nanoscopic needle emitter is utilized in a miniaturized electrostatic lens geometry as a high-brightness photoelectron source [1]. In a first application, we investigated phase-ordering kinetics in the structural transition between CDW-phases in 1T-TaS2 [2].
Here, we study collective phase-excitations of the incommensurate CDW state, so-called phasons. By a comparison of the pump-induced intensity suppressions of Bragg- and CDW-satellite-reflections, we determine the time-dependent temperature changes in the respective subsystems. Our results reveal a strong initial energy transfer to the phason system, followed by a long-lived non-equilibrium between phasons and phonons, indicating an inhibited electron-phason relaxation channel. We attribute this observation to a gap-induced decoupling of electron and phason systems.
[1] G. Storeck et al., Structural Dynamics 4.4, 044024 (2017). [2] S. Vogelgesang et al., Nature Physics (2017), advance online publication.