Berlin 2018 – wissenschaftliches Programm
O 101: Focus Session: Structural Dynamics in Nanoscale Materials, Probed by Ultrafast Electron Pulses II
O 101.4: Vortrag
Donnerstag, 15. März 2018, 16:30–16:45, HE 101
Phase-ordering kinetics of charge density waves mapped by ultrafast LEED — •Simon Vogelgesang1, Gero Storeck1, Jan Gerrit Horstmann1, Theo Diekmann1, Murat Sivis1, Sebastian Schramm1, Kai Rossnagel2, Sascha Schäfer1, and Claus Ropers1 — 1IV. Physical Institute - Solids and Nanostructures, University of Göttingen, Germany — 2Institute for Experimental and Applied Physics, University of Kiel, Germany
Recently, ultrafast low-energy electron diffraction was developed for the investigation of structural dynamics in thin films in a transmission geometry . In order to extend this approach to back-scattering diffraction for the analysis of surface dynamics, we employ miniaturized laser-driven electron sources featuring nanometric metal tip photocathodes . Here, we investigate dynamics of charge density wave (CDW) phases at the surface of the quasi-two-dimensional material 1T-TaS2 . Specifically, we trace the laser-induced transition from the room-temperature nearly-commensurate (NC) to the high temperature incommensurate (IC) CDW phase. Performing a thorough spot-profile analysis, we identify a coarsening behavior in the newly created IC phase exhibiting significant CDW disorder. This growth of the IC CDW coherence length is attributed to the annihilation of dislocation-type topological defects, as corroborated by numerical simulations in a Ginzburg-Landau approach.
 M. Gulde et al., Science 345, 200 (2014).  G. Storeck et al., Structural Dynamics 4, 044024 (2017).  S. Vogelgesang et al., Nature Physics (2017), advance online publication, doi:10.1038/nphys4309.