Dresden 2011 – scientific programme

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O: Fachverband Oberflächenphysik

O 43: Surface Dynamics II

O 43.3: Talk

Wednesday, March 16, 2011, 11:45–12:00, WIL B122

Optical-induced CDW-phase-transition in 1T-TiSe₂ probed by Time-Resolved High Harmonic Photoemission — •Timm Rohwer¹, Stefan Hellmann¹, Martin Wiesenmayer¹, Christian Sohrt¹, Ankatrin Stange¹, Matthias Kalläne¹, Stefan Mathias², Kai Rossnagel¹, Lutz Kipp¹, and Michael Bauer¹ — ¹Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel — ²JILA, University of Colorado and NIST, Boulder, USA

Time- and angle-resolved photoemission was employed to monitor the ultrafast dynamics consequent to the photoexcitation of a charge density wave (CDW) phase in the transition metal dichalcogenide 1T-TiSe₂. The application of XUV high harmonic pulses (43 eV) allows us to record photoemission transients covering the full size of the first Brillouin zone. The excitation fluence dependence of the ultrafast breakdown of a (2×2×2) superstructure characteristic for the 1T-TiSe₂ CDW phase was investigated and response times up to values less than 30 fs were observed. The origin of this breakdown is assigned to a build up of electronic screening by the transient generation of free charge carriers.