Regensburg 2019 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 80: Ultrafast Electron Dynamics at Surfaces and Interfaces I
O 80.7: Vortrag
Donnerstag, 4. April 2019, 12:00–12:15, H16
Probing non-equilibrium lattice excitations in 1T-TaS2 by ultrafast LEED — •Gero Storeck1, Theo Diekmann1, Gerrit Horstmann1, Simon Vogelgesang1, Kai Rossnagel2, and Claus Ropers1 — 14th Physical Institute - Solids and Nanostructures, University of Göttingen, Germany — 2Institute for Experimental and Applied Physics, University of Kiel, Germany
Transition-metal dichalcogenides (TMDCs) exhibit a multitude of correlation-induced states, such as charge-density wave (CDW) phases coupled to a periodic lattice distortion (PLD). Optical excitation of these states leads to a transient quench of the CDW gap and the excitation of various fluctuation modes. While the Raman-active amplitude modes lead to strong signatures in optical spectroscopy and are frequently observed in photoelectron spectroscopy, phason excitations remain more elusive [1,2].
Here, we present an ultrafast low-energy electron diffraction (ULEED) study of the incommensurate and nearly commensurate CDW phases of 1T-TaS2 [3]. We trace the non-equilibrium dynamics of the CDW amplitude, and study the population of phonon and phason modes by their influence on the diffraction intensity of the lattice Bragg peaks, the PLD satellite peaks as well as the diffuse background scattering.
[1] Lee, W. S. et al., Nature Communications 3, (2012).
[2] Liu, H. Y. et al., Physical Review B 88, (2013).
[3] Wilson et al., Advances in Physics 24, 117-201 (1975).