Electrically tunable spoof plasmonic metamaterial for independent control of electric and magnetic resonances

A single ultra-thin multi-arm metal spiral structure (MSS) can simultaneously support strong electric and magnetic resonances in the deep subwavelength region without an external magnetic field source, which is particularly interesting in electromagnetic wavefront manipulation. However, independent control of electric resonance or magnetic resonance remains a challenge. Here, we propose an electrically tunable plasmonic metamaterial that allows dynamic modulation of both electric and magnetic resonances. The flexibility in tuning these resonance modes is achieved by incorporating voltage-controlled varactors into the multi-arm MSS, which can support spoof localized surface plasmon modes. This scheme allows active tuning of the resonant mode sequence and selective excitation of higher-order modes. Through the optimization of loading position and DC feed voltage of the varactors, the analytical, numerical, and experimental results consistently show the effectiveness of the tuning of multimodal resonance. Our platform significantly enhances the controllability of localized surface plasmons, facilitating their applications in reconfigurable devices.