Geometry-dependent critical currents in superconducting nanocircuits
Author(s)Clem, John R.; Berggren, Karl K.
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In this paper, we calculate the critical currents in thin superconducting strips with sharp right-angle turns, 180∘ turnarounds, and more complicated geometries, where all the line widths are much smaller than the Pearl length Λ=2λ2/d. We define the critical current as the current that reduces the Gibbs-free-energy barrier to zero. We show that current crowding, which occurs whenever the current rounds a sharp turn, tends to reduce the critical current, but we also show that when the radius of curvature is less than the coherence length, this effect is partially compensated by a radius-of-curvature effect. We propose several patterns with rounded corners to avoid critical-current reduction due to current crowding. These results are relevant to superconducting nanowire single-photon detectors, where they suggest a means of improving the bias conditions and reducing dark counts. These results also have relevance to normal-metal nanocircuits, as these patterns can reduce the electrical resistance, electromigration, and hot spots caused by nonuniform heating.
DepartmentMassachusetts Institute of Technology. Department of Electrical Engineering and Computer Science
Physical Review B
American Physical Society
Clem, John, and Karl Berggren. “Geometry-dependent Critical Currents in Superconducting Nanocircuits.” Physical Review B 84.17 (2011): [27 pages].
Final published version