Evidence for low-field crossover in the vortex critical velocity of type-II superconducting thin films
G. Grimaldi, A. Leo, D. Zola, A. Nigro, S. Pace, F. Laviano, E. Mezzetti
DOI 10.1103/PhysRevB.82.024512 · Physical Review B
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Abstract
We measure current-voltage characteristics as function of magnetic field and temperature in Nb strips of different thickness and width. The instability voltage of the flux-flow state related to the vortex critical velocity v∗ is studied and compared with the Larkin-Ovchinnikov theory. Beside the usual power-law dependence v∗≈B−1/2, in the low-field range a new crossover field, Bcr1, is observed below which v∗ decreases by further lowering the external magnetic field B. We ascribe this unexpected crossover to vortex channeling due to a fanlike penetration of the applied magnetic field as confirmed by magneto-optic imaging. The observation of Bcr1 becomes a direct evidence of a general feature in type-II superconducting films at low fields that is a channel-like vortex motion induced by the inhomogeneous magnetic state caused by the relatively strong pinning.
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. | 7.6 | Pressure not reported | zero_resistance |
| Nb Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 8.2 | Pressure not reported | zero_resistance |
| Nb Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 8.1 | Pressure not reported | zero_resistance |
| Nb Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 8.5 | Pressure not reported | zero_resistance |
| Nb Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 8.7 | Pressure not reported | zero_resistance |
| Nb Archive — visibility unverified Source-occurrence policy only; no material identity or catalogue acceptance is inferred from the formula. | 9.2 | Pressure not reported | zero_resistance |
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