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DS: Fachverband Dünne Schichten

DS 44: Postersession II

DS 44.47: Poster

Donnerstag, 23. März 2017, 17:00–19:00, P1C

Time-resolved THz spectroscopy on 1T-TaS₂ — •Simon Lange¹, Lara Wimmer¹, Georg Herink¹, Kai Rossnagel², and Claus Ropers¹ — ¹4th Physical Institute - Solids and Nanostructures, University of Göttingen, Friedrich-Hund-Platz 1, Germany — ²Institute for Experimental and Applied Physics, University of Kiel, Leibnizstraße 15, Germany

Transition metal dichalcogenides (TMDCs) are a highly interesting class of materials due to their two-dimensional behaviour, which leads to multiple phenomena, like Mott and Peierls transitions, superconductivity and charge and spin density waves. A prominent representative of TMDCs, 1T-TaS₂, shows various different charge density wave (CDW) phases associated with periodic lattice distortions.

Here, we present an optical pump/terahertz probe setup in a transmission geometry for characterizing the ultrafast response of materials in the spectral range of 0.5 to 3 THz and at temperatures between 130 to 300 K.

Using this setup, in temperature-dependent measurements, we observe the phase transition between the commensurate (C) and nearly-commensurate (NC) charge density wave phases and its hysteresis in a 1T-TaS₂ thin film. We identify three characteristic phonon modes in the insulating C phase, which vanish in the metallic NC phase [1]. In time-resolved measurements (see also Ref. [2]), we optically induce this transition and track the evolution of the phonon modes.

[1] L. Gasparov, Phys. Rev. B, 66, 094301 (2002)

[2] N. Dean et al., Phys. Rev. Lett. 106, 016401 (2011)