Symmetry of the superconducting order parameter in a YBa2Cu3O7−δ epitaxial films

Abstract

We propose a way to measure the interference associated with two superconductors with a ${\mathit{d}}_{\mathit{x}}^2$-${\mathit{y}}^2$ symmetry coupled by a Josephson weak link. An experimental realization shows no interference effects in a superconducting ${\mathrm{YBa}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$ film. The results are consistent with s-wave symmetry.