Berlin 2018 – scientific programme
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DY: Fachverband Dynamik und Statistische Physik
DY 35: Nonequilibrium Quantum Many-Body Systems I (joint session TT/DY)
DY 35.2: Talk
Wednesday, March 14, 2018, 10:00–10:15, H 3010
Photoinduced non-thermal insulator-to-metal transition in NbO2 epitaxial thin films — •Rakesh Rana1, John Klopf1, Joerg Grenzer1, Harald Schneider1, Manfred Helm1,2, and Alexej Pashkin1 — 1Helmholtz-Zentrum-Dresden-Rossendorf, 01328 Dresden, Germany — 2Technische Universität Dresden, 01062 Dresden, Germany
The ultrafast insulator-to-metal transition in the correlated oxides such as vanadium dioxide (VO2) has been extensively explored for its rich physics and potential applications. In this regard, its isovalent counterpart niobium dioxide (NbO2) with considerably higher transition temperature (TC = 1080 K) can be envisaged as a potential alternative. We have performed time-resolved optical pump-terahertz (THz) probe measurements on NbO2 epitaxial thin-film at room temperature. The onset of the THz conductivity is followed by an exponential decay on a timescale of 400 fs. The photoinduced change in THz transmission at later delay times exhibits an excitation threshold of 17.5 mJ/cm2. Notably, in contrast to VO2, the pump energy required for the switching into a metastable metallic state is smaller than the energy necessary for heating NbO2 up to TC providing strong evidence for the non-thermal character of the photo induced insulator-to-metal transition in this system. The transient optical conductivity in the metastable state can be modelled using the Drude model confirming its metallic character.