Optical-pump terahertz-probe spectroscopy is used to investigate ultrafast far-infrared conductivity dynamics during the insulator-to-metal transition in vanadium sesquioxide $\left({\mathrm{V}}_2{\mathrm{O}}_3\right)$. The resultant conductivity increase occurs on a tens of picosecond time scale, exhibiting a strong dependence on the initial temperature and fluence. We have identified a scaling of the conductivity dynamics upon renormalizing the time axis with a simple power law $\left(\alpha \simeq 1/2\right)$ that depends solely on the initial, final, and conductivity onset temperatures. Qualitative and quantitative considerations indicate that the dynamics arise from nucleation and growth of the metallic phase which can be described by the Avrami model. We show that the temporal scaling arises from spatial scaling of the growth of the metallic volume fraction, highlighting the self-similar nature of the dynamics. Our results illustrate the important role played by mesoscopic effects in phase transition dynamics.

• Received 24 October 2014
• Revised 5 February 2015

DOI:https://doi.org/10.1103/PhysRevB.92.085130