Comparison of the superconducting pairing between the oxide superconductors Ba1-xKxBiO3 and YBa2CU3O6.6 using phase-sensitive Josephson tunneling

We compare the Josephson tunneling of a suspected d-wave superconductor, YBa2Cu3O6.6, with that of another oxide superconductor Ba1-xKxBiO3, For comparison the critical current I-c vs applied field of a single-crystal Josephson junction injecting supercurrent in the [110] direction is measured for both superconductors. For the YBa2Cu3O6.6 single crystal (T-c=60 K), the critical current is a minimum at zero applied field, while for Ba1-xKxBiO3, the critical current reveals a maximum at zero field. The results are consistent with ad-wave order parameter for YBa2Cu3O6.6, and conventional s-wave superconductivity for Ba1-xKxBiO3.