<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi mathvariant="italic">c</mml:mi></mml:math>-axis Josephson Tunneling between<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi>YBa</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow><mml:mrow><mml:msub><mml:mrow><mml:mi>Cu</mml:mi></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub></mml:mrow><mml:mrow><mml:msub><mml:mrow><mml:mi>O</mml:mi></mml:mrow><mml:mrow><mml:mn>7</mml:mn><mml:mo>−</mml:mo><mml:mi>δ</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math>and Pb: Direct Evidence for Mixed Order Parameter Symmetry in a High-<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi>T</mml:mi></mml:mrow><mml:mrow><mml:mi>c</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math>Superconductor
K. Kouznetsov(Lawrence Berkeley National Laboratory), A. G. Sun(University of California, San Diego), B. Chen(Lawrence Berkeley National Laboratory), A. S. Katz(University of California, San Diego), Safi R. Bahcall(Lawrence Berkeley National Laboratory), John Clarke(Lawrence Berkeley National Laboratory), R. C. Dynes(University of California, San Diego), D. A. Gajewski(University of California, San Diego), Seung Ho Han(University of California, San Diego), M. B. Maple(University of California, San Diego), J. Giapintzakis(University of Illinois Urbana-Champaign), J.-T. Kim(University of Illinois Urbana-Champaign), D. M. Ginsberg(University of Illinois Urbana-Champaign)
Cited by 192Open Access
Abstract
We report a new class of $c$-axis Josephson tunneling experiments in which a conventional superconductor (Pb) is deposited across a single twin boundary of a $\mathrm{YBa}{}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7\ensuremath{-}\ensuremath{\delta}}$ (YBCO) crystal. We measure the critical current as a function of the magnitude and angle of a 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 $d$- and $s$-wave pairing in YBCO, with a reversal in the sign of the $s$-wave component across the twin boundary.
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