Strain-induced anisotropy in VO$_{2}$ film for metamaterial resonance switching and frequency tuning*

Vanadium dioxide (VO$_{2})$ undergoes fascinating first order insulator-to-metal phase transition (IMT) around 68 $^{\circ}$C. We demonstrate VO$_{2}$ that thin-films grown on Si substrate exhibit strain induced metallic streaks that are unidirectional during IMT. We unveil the nanoscale formation and spatial dynamics of these streaks and further use the unique anisotropic property of the VO$_{2}$ film to dynamically tune the metamaterial resonances. We reveal thermal control of the metamaterial infrared resonances by nanoscale spatial near-field imaging of both the metallic streaks phase evolution on VO$_{2}$ film and the resonance states of the metamaterial.