Fig. 2: Characteristics of superconductivity under resonant plasmon excitation.

a Voltage–current (V-I) characteristics of device A1 (AuNPs/hBN/NbSe₂) on a logarithmic scale at various photon fluxes. The black dashed line denotes the expected V ~ I³ behavior for the BKT transition. b, c Photon flux dependence of the superconducting gap size Δ and critical current I_c. Δ is extracted by fitting the differential conductance spectra, dI/dV versus V, within the Blonder-Tinkham-Klapwijk model (Supplementary Fig. 12). I_c is extracted from the superconducting-to-normal transitions in (a). The linear fittings are guides to the eye. d Sample resistance as functions of perpendicular magnetic field B and photon flux N. e Photon flux dependence of the critical field B_c, extracted from (d). The power fitting is the guide to the eye. All the data in a-e are taken at a temperature of 2.2 K. f Temperature dependence of the critical field B_c without and with plasmon excitation (N = 1.56 × 10¹³ s⁻¹mm⁻²), extracted from the mappings of resistance versus temperature and magnetic field in Supplementary Fig. 15. The linear fittings give Ginzburg–Landau coherence lengths ξ_GL of 11.8 and 13.5 nm without and with plasmon excitation, respectively. B_c in (e) and (f) are defined by the field at which R reaches 50% of the normal state resistance. The measurements are taken with two-terminal configuration, same to Fig. 1. A contact resistance R_c = 54.5 Ω has been deducted.