Mid‐infrared Plasmonic Resonances in 2D VO₂ Nanosquare Arrays

Plasmon resonances on 2D nanosquare arrays and their temperature‐dependent modulations are demonstrated using the insulator‐to‐metal transition (IMT) of VO₂. A comparison between observed experimental trends and electromagnetic simulations reveals that the plasmon coupling is effective in the periodic 2D alignment of metallic VO₂ nanosquares and results in a collective plasmon excitation. This plasmon excitation affects the optical responses of VO₂ nanosquares in the mid‐infrared (IR) range through reduction of plasmon damping in relation to the specific band structure of VO₂. This preliminary understanding is important for the elucidation of temperature‐dependent plasmon resonances. The IMT of VO₂ produces temperature‐dependent plasmon resonances with respect to spectral features. The electrodynamic simulations reveal that these phenomena are based on plasmon coupling in the nanosquare array when each nanosquare acts as a single metallic domain. The hysteretic plasmon resonances are derived from resonant coupling between metallic VO₂ nanosquares via the IMT nature of VO₂, which results in temperature‐dependent changes in collective plasmon excitations in the nanosquare array.