Reversible modulation of superconductivity in thin-film NbSe₂ via plasmon coupling

In recent years, lightwave has stood out as an ultrafast, non-contact control knob for developing compact superconducting circuitry. However, the modulation efficiency is limited by the low photoresponse of superconductors. Plasmons, with the advantages of strong light-matter interaction, present a promising route to overcome the limitations. Here we achieve effective modulation of superconductivity in thin-film NbSe₂ via near-field coupling to plasmons in gold nanoparticles. Upon resonant plasmon excitation, the superconductivity of NbSe₂ is substantially suppressed. The modulation factor exceeds 40% at a photon flux of 9.36 × 10¹³s^-1mm^-2, and the effect is significantly diminished for thicker NbSe₂ samples. Our observations can be theoretically interpreted by invoking the non-equilibrium electron distribution in NbSe₂ driven by the plasmon-associated evanescent field. Finally, a reversible plasmon-driven superconducting switch is realized in this system. These findings highlight plasmonic tailoring of quantum states as an innovative strategy for superconducting electronics.