Berlin 2018 – wissenschaftliches Programm

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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: Vortrag

Mittwoch, 14. März 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 Helm^1,2, 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 (T_C = 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 T_C 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.