Figure 2: Josephson current–voltage characteristics.

I(V)-characteristics of the Josephson effect for two different Al tips on an Al(100) sample. The tunnel junctions in (a) and (b) have a capacitance of 3.5 fF and 7 fF, respectively, which means that the tunnel junction in (a) is more sensitive to the surrounding environment. Therefore, the principal impedance resonance ω₀ is visible in (a) and not in (b). The fit using P(E)-theory (black lines) is in excellent agreement with the data. The P(E)-functions extracted from the fits in (a) and (b) are shown on a linear scale in (c) and on a logarithmic scale in (d). The asymmetry of the P(E)-function is clearly visible.