Fig. 2: Josephson effect.
From: Superconducting quantum interference at the atomic scale
a, Josephson spectra I(V) in a range of ±60 μeV, shifted horizontally by the conductance at which they were measured. The horizontal bracket indicates the region where the evolution deviates from the conventional Ambegaokar–Baratoff formula. The QPT is indicated by the vertical dashed line. b, The switching current IS, which is the current maximum indicated in a as function of the normal state conductance GN (blue line). The square dependence at low and high conductance is indicated by dashed lines (labelled \({\propto }{G}_{{{{\rm{N}}}}}^{2}\)). The YSR energy as a function of conductance is shown as a blue line. The minimum indicates the QPT (vertical dashed line). The YSR state energy (red line) is plotted for comparison. The minimum indicates the QPT. c, \({\sqrt{{I}_{{{{\rm{S}}}}}}}{R}_{{{{\rm{N}}}}}\) (blue line) of the data in b, which is proportional to ICRN for a harmonic energy–phase relation (RN, renormalized resistance (see text); IC, critical current). A reference junction without any YSR states is shown as an orange line, indicating the expected evolution according to the Ambegaokar–Baratoff formula.
