Vortex pinning by disordered columnar defects in large Josephson junctions

Abstract

To study the pinning of Josephson vortices by well-characterized correlated disorder, we have fabricated and made measurements on a series of large Josephson junctions with lithographically defined parallel columnar defects arranged with varying degrees of positional disorder. Commensurability between vortices and a periodic array of defects gives rise to sharp peaks in Ic(H). Randomly shifting the defects from initially periodic positions causes the decay of these commensurate peaks as well as the emergence of a randomly fluctuating background with an oscillatory envelope. Completely random defect placement induces similar Ic fluctuations with weaker envelope oscillations. Using a model based on the blocking of Josephson currents by the defects, we have performed numerical calculations which accurately reproduce Ic(H) for any given defect configuration and provide a physical understanding of its essential features.

Source-reported materials — not catalogue approval

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