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C-axis Josephson Tunneling Between YBCO and Pb: Direct Evidence for Mixed Order Parameter Symmetry in a High-T_c Superconductor

arXiv:cond-mat/9705283 · doi:10.1103/PhysRevLett.79.3050

Abstract

We report a new class of -axis Josephson tunneling experiments in which a conventional superconductor (Pb) is deposited across a single twin boundary of a YBa_2Cu_3O_{7-δ} crystal. We measure the critical current as a function of magnitude and angle of magnetic field applied in the plane of the junction. In all samples, we observe a clear experimental signature of an order parameter phase shift across the twin boundary. These results provide strong evidence for mixed - and -wave pairing in YBCO, with a reversal in the sign of the -wave component across the twin boundary.

4 pages RevTex, 4 postscript figures included, submitted to Phys. Rev. Lett

C-axis Josephson Tunneling Between YBCO and Pb: Direct Evidence for Mixed Order Parameter Symmetry in a High-T_c Superconductor · wovepaper