WEAK-LINK BETWEEN CONVENTIONAL AND UNCONVENTIONAL SUPERCONDUCTORS

In this paper we consider the Josephson coupling between a conventional and an unconventional superconductor through a constriction. It is demonstrated that a weak link is very different from a tunnel junction. In particular, in an orientation where the coupling in a tunnel junction vanishes because of symmetry, the Josephson current in the case of a weak link can nevertheless be finite, albeit with the distinctive characteristics of (i) a current phase relationship with a period of 2pi/n, (ii) the critical current near but below the transition temperature T1 of the lower transition temperature superconductor is proportional to (1 - (T/T1))n/2, Where n is an integer determined by the symmetry.