Regensburg 2010 – scientific programme

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O: Fachverband Oberflächenphysik

O 5: Electron and spin dynamics I

O 5.7: Talk

Monday, March 22, 2010, 12:45–13:00, H34

1T-TiSe₂: Ultrafast Dynamics in the CDW Phase — •Stephan Hilgenfeldt, Martin Wiesenmayer, and Michael Bauer — Institut für Experimentelle und Angewandte Physik, Universität Kiel, 24098 Kiel, Germany

At T≈ 200 K the transition metal dichalcogenide 1T-TiSe₂ undergoes a phase transition into a charge density wave (CDW) phase which is accompanied by the formation of a (2×2×2) superlattice. The origin of this CDW phase has been under discussion for a long time and recent photoemission experiments give evidence for an excitonic insulator phase to play a key role in the understanding of this system. In this talk we present pump-probe photoemission results of 1T-TiSe₂ in the CDW state in the weak excitation regime. We are able to monitor an optically induced weakening of the CDW phase taking place within 250 fs and we follow the subsequent dynamics of this perturbation further into the picosecond time regime. Our results will be discussed under consideration of the excitonic insulator model for TiSe₂.