Evidence for a structurally-driven insulator-to-metal transition in VO 2 : A view from the ultrafast timescale

We apply ultrafast spectroscopy to establish a time-domain hierarchy between structural and electronic effects in a strongly correlated electron system. We discuss the case of the model system ${\mathrm{VO}}_{2}$, a prototypical nonmagnetic compound that exhibits cell doubling, charge localization, and a metal-insulator transition below 340 K. We initiate the formation of the metallic phase by prompt hole photo-doping into the valence band of the low-$T$ insulator. The insulator-to-metal transition is, however, delayed with respect to hole injection, exhibiting a bottleneck time scale, associated with the phonon connecting the two crystallographic phases. This structural bottleneck is observed despite faster…

• UD
  U.S. Department of Energy

  Awards: AC03-76SF00098, DE-AC03-76SF00098, DE-AC03
• OO
  Office of Science

  Award: DE-AC03-76SF00098
• BE
  Basic Energy Sciences

  Awards: AC03-76SF00098, DE-AC03-76SF00098