Evidence for a Percolation-Driven Transition to Coherent Surface Superconductivity
Jürgen Kötzler, Lars von Sawilski, Sara Casalbuoni
DOI 10.1103/PhysRevLett.92.067005 · Physical Review Letters
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Abstract
Above the upper critical field we have investigated the field dependences of the surface conductance, G′−iG′′, and the critical current Jc of an electropolished pure niobium cylinder. The low frequency limits of G′, G′′, and Jc display power-law singularities, defining a transition to coherent surface superconductivity at Hc3c. The critical exponents as well as the dynamical scaling of G′−iG′′ are consistent with predictions for a two-dimensional percolation transition. Relating Hc3c to the conventional onset field, we find Hc3c/Hc3=0.81, and, surprisingly, this ratio turns out to be independent of significant variations of Hc3 due to differently structured surfaces.
Source-reported materials — not catalogue approval
| Formula | Reported Tc (K) | Pressure (GPa) | Type |
|---|---|---|---|
| Nb Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | — | Pressure not reported | unknown |
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