Critical current of a lateral Josephson junction for layered superconductors

Abstract

We have studied the effect of an applied magnetic field Hext on the critical current Ic of a lateral superconducting-insulating-superconducting (S-I-S) Josephson junction between two layered superconductors. In this configuration the layering direction of the superconducting electrodes is parallel to the plane of the junction. We find that the behavior of Ic(Hext) is determined by the parameter δ=jcd0/λ⊥j⊥, where λ⊥ and j⊥ are, respectively, the penetration depth and the interlayer critical current characterizing the bulk superconductors. Also jc is the critical current density between layers on opposite sides of the junction, while d0 is the layer thickness. For δ≪1 the length scale for field penetration along the direction of the junction is given by λ⊥, leading to the usual Fraunhofer dependence for Ic(Hext). The scenario is vastly different for δ≥1. In this case the intraelectrode layer couplings are relatively weak and Josephson vortex penetration is found to occur between the layers. The physics of this situation is determined by the standard map. We find that in the absence of an external field Josephson vortices penetrate the structure and form an ordered array. This leads to a value of Ic(0) proportional to the number of layers N. This situation is however upset by a small external field. In this case the vortex distribution acquires an interesting chaotic character which leads to a sizable decrease of the critical current to a value Ic(Hext)∝ √N .

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