Berlin 2015 – scientific programme

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O: Fachverband Oberflächenphysik

O 69: Ultrafast Electron and Spin Dynamics

O 69.2: Poster

Wednesday, March 18, 2015, 18:15–21:00, Poster A

Femtosecond time- and angle-resolved photoemission spectroscopy of 1T-TaSe₂ — •Florian Diekmann, Christian Sohrt, Ankatrin Stange, Michael Bauer, and Kai Rossnagel — Institut für Experimentelle und Angewandte Physik Universität Kiel, D-24098 Kiel

According to previous angle-resolved photoemission spectroscopy and scanning tunneling microscopy studies, the surface of 1T-TaSe₂ displays combined Peierls-Mott insulating behavior for temperatures below about 260-300 K, while bulk sensitive resistivity measurements show metallic character and no indication for a Mott transition [1]. Here, we use time- and angle-resolved extreme ultraviolet photoemission spectroscopy to directly determine the momentum-dependent electronic structure dynamics of this surface phase on the femtosecond time scale [2]. The extracted spectroscopic order parameters reveal a global two-time-scale dynamics indicating a quasi-instantaneous loss of the Mott and charge-density-wave electronic orders and a subsequent coherent suppression of the lattice distortion on a time scale related to the frequency of the charge-density-wave amplitude mode. Specifically after one half-cycle of coherent amplitude-mode vibration, a crossover state between insulator and metal with partially filled-in and partially closed Mott and Peierls gaps is reached.

[1] L. Perfetti et al., Phys. Rev. Lett. 90, 166401 (2003).

[2] C. Sohrt et al., Faraday Discuss. 171, 243 (2014).