THz induced insulator to metal transition in VO$_{2}$ metamaterial

We use metamaterial enhanced high field terahertz (THz) pulses (up to $\sim $4MV/cm) to induce the insulator-to-metal transition in vanadium dioxide (VO$_{2})$ thin films at 320K. Ultrafast THz field enhancement in the gaps of metamaterial split ring resonators releases free electrons in VO$_{2}$ by the Poole-Frenkel effect. The accelerated hot electrons transfer energy to the lattice via electron phonon coupling inducing the persistent metallic phase. A large nonlinear signature is observed in VO$_{2}$ as modulations of the metamaterial resonance on a picosecond time scale. Our results provide insight into electric field induced phase transitions in VO$_{2}$ and paves the way for studying nonlinear high THz field effects in many other strongly correlated materials.