Workshop on Ultrafast Dynamics in Strongly Correlated Systems

Ultrafast changes in lattice symmetry probed by coherent phonons in VO2

4 Apr 2011, 15:30

20m

ETH Zurich, Campus Science City, HIT Building

Talk Electrons and phonons

Speaker

Simon Wall (Fritz Haber Institute)

Description

The effect of an ultrafast change in crystal symmetry on the coherent response of the lattice is investigated using the photoinduced semiconductor-metal phase transition in VO2. Below the photoinduced phase transition threshold, the four lowest Ag phonon modes of the monoclinic phase modulate the transient reflectivity. As the pump intensity is increased, a photoinduced phase transition occurs resulting in a prompt change in the phonon dynamics. These measurements observe lattice dynamics on a timescale previously inaccessible to current lattice probes and show that the photoinduced phase transition is driven by excited electrons changing the lattice potential symmetry.