SKM 2023 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 34: Ultrafast Electron Dynamics at Surface and Interfaces III
O 34.5: Vortrag
Dienstag, 28. März 2023, 11:30–11:45, TRE Phy
Resolving momentum-dependent phonon buildup at a 1T-TiSe2 surface using diffuse scattering in ultrafast LEED — •Felix Kurtz1, Tim Dauwe1, Sergey Yalunin1, Gero Storeck2, Jan Gerrit Horstmann1, Hannes Böckmann-Clemens1, and Claus Ropers1,2 — 1Max Planck Institute for Multidisciplinary Sciences, Am Fassberg 11, D-37077 Göttingen — 24th Physical Institute, University of Göttingen, Friedrich-Hund-Platz 1, D-37077 Göttingen
Electron-phonon and phonon-phonon couplings govern the energy flow into and within the lattice following femtosecond laser excitation. The resulting transient phonon population can be directly deduced from momentum-resolved maps in ultrafast electron diffuse scattering [1]. Here, we employ ultrafast low-energy electron diffraction (ULEED) [2] to investigate structural dynamics and pathways for energy relaxation in the optically-excited charge-density-wave phase of 1T-TiSe2. By analyzing the diffuse scattering background, we track the nonequilibrium evolution of the phonon population and observe strongly momentum-dependent rise times. Specifically, we find a rapid buildup of zone-boundary phonons within few picoseconds, followed by a substantially slower generation of low-energy zone-center acoustic phonons. Our findings are corroborated by ab-initio DFT calculations of phonon-phonon scattering rates. We believe that the presented approach is generally applicable to a variety of systems and provides fundamental insights into surface phonon dynamics and relaxation pathways.
[1] L. P. René de Cotret, et al., Phys. Rev. B 100, 214115 (2019)
[2] G. Storeck, et al., Structural Dynamics 7, 034304 (2020)