Regensburg 2016 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 71: 2D Materials beyond Graphene -Dynamics and Excitation
(Joint session of DS, DY, HL, MA, O and TT organized by O)
TT 71.11: Vortrag
Donnerstag, 10. März 2016, 13:15–13:30, S054
Charge density wave kinetics in 1T-TaS2 monitored by ultrafast LEED — •Simon Schweda1, Gero Storeck1, Sebastian Schramm1, Max Gulde1, Kai Roßnagel2, Sascha Schäfer1, and Claus Ropers1 — 1IV. Physikalisches Institut, Universität Göttingen, D-37077 Göttingen — 2Institut für Experimentelle und Angewandte Physik, Universität Kiel, D-24098 Kiel
We developed an ultrafast low-energy electron diffraction (ULEED) setup for the study of time-resolved structural dynamics at surfaces, extending our previous approach operating on ultrathin films in transmission [1]. A laser-driven nanometric needle emitter provides well-collimated electron pulses with durations of few tens of ps at the sample for electron energies in the range of 50-200 eV.
In a first application of this technique, we investigate optically induced transitions between charge density wave (CDW) phases [2] at a single-crystalline 1T-TaS2 surface. In particular, the recovery of the nearly commensurate (NC) room-temperature phase after laser-excitation to the incommensurate (IC) phase is resolved in the time-domain. We find a strong dependence of the formation time on the energy density deposited. Furthermore, at higher optical fluences, the appearance of metastable NC antiphase domains is observed, caused by a rapid quench after optical excitation. Our results demonstrate the potential of ULEED for the study of complex ultrafast structural and electronic processes at surfaces.
[1] M. Gulde et al., Science 345, 200 (2014)
[2] M. Eichberger et al., Nature 468, 799 (2010)