Enhanced photosusceptibility near Tc for the light-induced insulator-to-metal phase transition in vanadium dioxide.
We use optical-pump terahertz-probe spectroscopy to investigate the near-threshold behavior of the photoinduced insulator-to-metal (IM) transition in vanadium dioxide thin films. Upon approaching Tc a reduction in the fluence required to drive the IM transition is observed, consistent with a softening of the insulating state due to an increasing metallic volume fraction (below the percolation limit). This phase coexistence facilitates the growth of a homogeneous metallic conducting phase following superheating via photoexcitation. A simple dynamic model using Bruggeman effective medium theory describes the observed initial condition sensitivity.
Hilton
D J
DJ
Center for Integrated Nanotechnologies, MS K771, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
Prasankumar
R P
RP
Fourmaux
S
S
Cavalleri
A
A
Brassard
D
D
El Khakani
M A
MA
Kieffer
J C
JC
Taylor
A J
AJ
Averitt
R D
RD