Vortex depinning in Josephson-junction arrays

E. K. F. Dang; B. L. Györffy

doi:10.1103/PhysRevB.47.3290

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Vortex depinning in Josephson-junction arrays

E. K. F. Dang, B. L. Györffy

DOI 10.1103/PhysRevB.47.3290 · Physical Review B

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Abstract

On the basis of a simple model we study the supercurrent-carrying capacity of a planar array of Josephson junctions. In particular we investigate the zero-temperature vortex-depinning current icB, which is the largest supercurrent in an array containing one extra vortex on top of the ground-state vortex superlattice induced by an external magnetic field f. In the zero-field, f=0, case our results support the tilted-sinusoidal vortex-potential description of previous workers. However, in the fully frustrated, f=1/2 case, a more careful interpretation is required. We find that on the application of a transport current, the resulting vortex motion is not that of the extra vortex moving over a rigid field-induced vortex background. Rather, a vortex belonging to the checkerboard ground-state pattern first crosses over a junction into a neighboring ‘‘empty’’ plaquette. Then, the ‘‘extra’’ vortex moves to take its place. Our interpretation is based on a linear stability analysis, with the onset of vortex motion being associated with the vanishing of one eigenvalue of the stability matrix. Further applications of the method are suggested.