Berlin 2012 – scientific programme

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O: Fachverband Oberflächenphysik

O 8: Electron and spin dynamics

O 8.4: Talk

Monday, March 26, 2012, 11:15–11:30, A 060

Ultrafast melting of a charge-density wave in the Peierls insulator Rb:TaS₂ — •Kerstin Hanff, Stefan Hellmann, Timm Rohwer, Michael Bauer, Lutz Kipp, and Kai Rossnagel — Institute of Experimental and Applied Physics, University of Kiel, 24098 Kiel, Germany

Ultra-short high-harmonic pulses enable us to study ultrafast dynamics of condensed matter systems on femto- and picosecond time scales. In particular, they allow us to identify the nature and strength of interactions between various degrees of freedom in complex materials, in which typically two or more of the lattice, charge, spin and orbital degrees of freedom are strongly coupled. Our recent studies focused on the investigation of electronically driven charge-density waves employing time- and angle-resolved photoelectron spectroscopy. Here, we present the ultrafast dynamics of a lattice driven CDW system. Rb adsorption on 1T–TaS₂ serves as a model system revealing a pronounced metal-to-insulator transition. Induced by a charge transfer, this intercalation process leads to a structural change into a commensurate CDW phase. Upon strong photoexcitation by an optical pump pulse the electronic gap closes and the Peierls insulator Rb:TaS₂ undergoes a transition into a transient metallic state. We are able to distinguish different time scales during the excitation and relaxation processes, which indicate the influence of the electronic and lattice systems.