Fig. 2: Switching statistics with temperature suggests inhomogeneities and competing order.
a, The Vd.c.–Id.c. characteristics of a JJ showing the different switching currents. b, The tilted washboard potential captures the JJ switching from the superconducting state to the normal state by an analogous picture of a particle crossing the potential barrier ΔU. Larger current biases (identified by symbols in a) tilt the washboard potential more, making it easier for the particle to cross the now-tilted barrier. Inset: the switching histogram showcases the stochastic nature of the JJ switching at different switching currents. c, To gather statistics of the switching current, a low-frequency triangular wave is applied by a function generator. The current varies linearly with time, starting from zero and reaching a value slightly above the critical current. The counter measures the elapsed time (ts) from the onset of zero-bias current (green dot) to the instance of transition from the superconducting state to the normal state (red dot). The ts value determines Is, considering the frequency and amplitude of the triangular signal. d, Switching histograms at the optimal hole-side doping and electric field (ν, D/ϵ0) = (–2.42, 0) as a function of temperature. The distributions evolve non-monotonically with temperature. The arrow represents the direction of temperature sweep. e, Mean current of the switching distributions \({I}_{{\rm{s}}}^{{\rm{mean}}}\) plotted as a function of temperature shows a non-monotonic behaviour. Inset: \({I}_{s}^{{\rm{mean}}}\) plotted with a temperature bin of 10 mK clearly shows the non-monotonic behaviour at (ν, D/ϵ0) = (–2.42, –0.29). The error bars denote the standard deviations of individual distributions of 10,000 data points each. f, Standard deviation normalized by the mean of the distributions \(\sigma /{I}_{{\rm{s}}}^{{\rm{mean}}}\) plotted as a function of temperature. The trend of the evolution of \(\sigma /{I}_{{\rm{s}}}^{{\rm{mean}}}\) with temperature denotes the different switching processes dominating at different temperatures. The initial temperature-independent MQT process (orange shading) transitions into the TA process (blue shading), where \(\sigma /{I}_{{\rm{s}}}^{{\rm{mean}}}\) increases. Inset: the washboard potential U varies as a function of phase Φ. The different switching processes—TA and MQT—are shown schematically, where ωp is the frequency of oscillation of the particle in the potential well.
