Volume 118, Number 2, April 2017
|Number of page(s)||6|
|Section||Condensed Matter: Electronic Structure, Electrical, Magnetic and Optical Properties|
|Published online||22 June 2017|
Ultrafast photo-induced dynamics across the metal-insulator transition of VO2
1 Department of Physics and Center for Advanced Nanoscience, University of California, San Diego La Jolla, CA 92093, USA
2 Materials Science and Engineering Program, University of California, San Diego - La Jolla, CA 92093, USA
3 Materials Sciences Division, Lawrence Berkeley National Laboratory - Berkeley, CA 94720, USA
4 Department of Physics, Universidad de los Andes - Bogotá 111711, Colombia
5 Raymond and Beverly Sackler School of Physics and Astronomy, Tel Aviv University - Tel Aviv 69978, Israel
6 School of Chemistry, the Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University Tel Aviv 69978, Israel
Received: 21 November 2016
Accepted: 5 June 2017
The transient reflectivity of VO2 films across the metal-insulator transition clearly shows that with low-fluence excitation, when insulating domains are dominant, energy transfer from the optically excited electrons to the lattice is not instantaneous, but precedes the superheating-driven expansion of the metallic domains. This implies that the phase transition in the coexistence regime is lattice-, not electronically-driven, at weak laser excitation. The superheated phonons provide the latent heat required for the propagation of the optically-induced phase transition. For VO2 this transition path is significantly different from what has been reported in the strong-excitation regime. We also observe a slow-down of the superheating-driven expansion of the metallic domains around the metal-insulator transition, which is possibly due to the competition among several co-existing phases, or an emergent critical-like behavior.
PACS: 71.30.+h – Metal-insulator transitions and other electronic transitions / 78.47.J- – Ultrafast spectroscopy (<1 psec)
© EPLA, 2017
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