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(a) Positive bias, , curves for sample A taken at with the switching current, , return current, , JNS, and PSC regimes indicated with arrows. Curve 1 (black) is measured at zero MW power and curves 2 (black) and 3 (red) are measured at and output MW powers at 3 GHz frequency. Inset: SEM image of sample A. (b) Normalized voltage, eV/hf vs. curves for the PSC regime in sample A for applied MW powers decreasing from top to bottom curves as follows (in decibels): , , , , and . These curves end where the wire switches to JNS. (c) Numerical simulations using the CPR given in the text for , , , , and , for decreasing from top curve to bottom curve as follows: 2.4, 2.0, 1.6, 0.8, and 0.6. The simulated curves show a similar shape to the experimental ones.
(a) for sample B taken at 9.5 GHz and 500 mK showing clear resonances. The boxed region represents the portion of the curve located between steps and . (b) The boxed region of the curve is shown here for various MW frequencies. The horizontal axis is (in arbitrary units). Each curve is shifted to line up with the MW frequency at which it was measured. The vertical axis is normalized voltage, 2 eV/hf. The frequencies starting from the left are (in gigahertz) as follows: 0.9, 2.7, 2.9, 5.4, 6.2, 8.2, 9.5, and 15. (c) Numerical simulation for all the resonances between the and steps using the CPR given by Eq. (2) as a function of the normalized frequency, , taken at and .
Schematic of the CPR used in numerical simulations. The CPR is shown as the black line, which represents supercurrent, , plotted versus the phase difference between the ends of the wire. When reaches , a phase slip occurs (indicated by the red arrows) and changes abruptly to a value given by the CPR at the resulting phase. Inset: Schematic multivalued representation of the same CPR. The solid curves are the stable branches which are separated by a phase difference of . The dotted line shows the unstable branches which are not used in our simulation. Here the red arrows show how a phase slip is equivalent to moving to the adjacent stable branch.
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