Figure 5

Experimental relation between \(d(\mathrm{ln}\,V)/d\mathrm{(1/}T)\) and the bias current I _b , for \(T\ll {T}_{c}\) for sample A, (a), and sample B, (b). The value of \(d(\mathrm{ln}\,V)/d\mathrm{(1/}T)\) is obtained from the slope of the \(\mathrm{log}\,(V)-\mathrm{1/}T\) relation shown in Fig. 4(a,b), respectively. We consider the lowest four temperatures and the corresponding four experimental values of \(d(\mathrm{ln}\,V)/d\mathrm{(1/}T)\). The solid line is equation (9) with I _c (0) = 76 μA, U(0) = 11.9 meV for sample A, and I _c (0) = 120 μA, U(0) = 47.2 meV for sample B. The two values of the I _c (0) were extrapolated from the experimental data illustrated in Fig. 3.