Fig. 4

Residual supercurrent. a Switching current of the Shapiro step n = 0 (supercurrent branch) I₀ normalized to the zero-power critical current I_c versus rf power P_rf. I₀ is extracted from Fig. 3b. The residual supercurrent that remains at the first node k = 1 is noted \(I_0^{k = 1}\). b Evolution of \(I_0^{k = 1}\) normalized to \(I_{\mathrm{c}}^{4\pi }\) versus \(f_{{\mathrm{rf}}}{\kern 1pt} \tau _{\mathrm{J}}^{4\pi } = f_{{\mathrm{rf}}}\hbar {\mathrm{/}}eRI_{\mathrm{c}}^{4\pi }\) computed for various \(I_{\mathrm{c}}^{4\pi }{\mathrm{/}}I_{\mathrm{c}}\) ratios. All points collapse on a single curve. The black dashed line is a polynomial fit that enables to extract \(I_{\mathrm{c}}^{4\pi }\) from experimental parameters. Note that fluctuations of \(I_0^{k = 1}{\mathrm{/}}I_{\mathrm{c}}^{4\pi }\) around this dashed line stem from the limited sampling of the Shapiro maps computed