Critical Josephson current in a model Pb/YBa2Cu3O7−δ junction

Abstract

We consider a simple model for a c-axis Pb/YBa2Cu3O7−δ Josephson junction. The observation of a nonzero current in such a junction by Sun et al. [Phys. Rev. Lett. 72, 2267 (1994)] has been taken as evidence against d-wave superconductivity in YBa2Cu3O7−δ. We suggest, however, that the pairing interaction in the CuO2 planes may well be d wave but that the CuO chains destroy the tetragonal symmetry of the system. We examine two ways in which this happens. In a simple model of an incoherent junction, the chains distort the superconducting condensate away from dx2-y2 symmetry. In a specular junction the chains destroy the tetragonal symmetry of the tunneling matrix element. In either case, the loss of tetragonal symmetry results in a finite Josephson current. Our calculated values of the critical current for specular junctions are in good agreement with the results of Sun and co-workers.

Source-reported materials — not catalogue approval

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