SUPERCONDUCTING PAIRING SYMMETRY AND JOSEPHSON TUNNELING

We study the relationship between the symmetry of the pairing state an d the temperature-dependent Josephson critical current J(c)(T) by gene ralizing the Ambegaokar-Baratoff theory to include tunneling between s uperconductors with various pairing states. We find that several appar ently contradictory experimental results, including Josephson tunnelin g along the c direction in YBCO/Pb junctions and phase shift measureme nts in YBCO/Pb de SQUIDs, can be consistently explained by assuming th at the pairing symmetry of YBCO is s + id with a dominant d-wave compo nent.