Untersuchung und Kontrolle Exzitonischer Quantenkorrelationen ( Emmy Noether)

  • FB Physik
    Pashkin, Alexej; Kübler, Carl; Ehrke, Henri; Lopez, Ricardo; Halabica, Andrej; Haglund, Richard; Huber, Rupert; Leitenstorfer, Alfred(2011): Ultrafast insulator-metal phase transition in VO2 studied by multiterahertz spectroscopy Physical Review B ; 83 (2011), 19. - ISSN 1098-0121

Ultrafast insulator-metal phase transition in VO<sub>2</sub> studied by multiterahertz spectroscopy

The ultrafast photoinduced insulator-metal transition in VO2 is studied at different temperatures and excitation fluences using multi-THz probe pulses. The spectrally resolved midinfrared response allows us to trace separately the dynamics of lattice and electronic degrees of freedom with a time resolution of 40 fs. The critical fluence of the optical pump pulse, which drives the system into a long-lived metallic state, is found to increase with decreasing temperature. Under all measurement conditions, we observe a modulation of the eigenfrequencies of the optical phonon modes induced by their anharmonic coupling to the coherent wave-packet motion of V-V dimers at 6.1 THz. Furthermore, we find a weak quadratic coupling of the electronic response to the coherent dimer oscillation resulting in a modulation of the electronic conductivity at twice the frequency of the wave-packet motion. The findings are discussed in the framework of a qualitative model based on an approximation of local photoexcitation of the vanadium dimers from the insulating state.

Forschungszusammenhang (Projekte)

Schwerpunktprogramm414/10keine Angabe
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Laufzeit: 15.12.2009 – 31.12.2010