Search for complex order parameter symmetry in Sr$_2$RuO$_4$ by Josephson interferometry experiments

We present the results of Josephson interferometry measurements on single crystals of the unconventional superconductor Sr$_{2}$RuO$_{4}$ designed to determine the order parameter symmetry by mapping out the phase anisotropy. A number of experiments suggest that this material has odd pairing symmetry and may exhibit an in-plane complex order parameter of the form p$_{x}$+ip$_{y}$. To test this, we have carried out measurements of the critical current vs. magnetic field in single junctions and dc SQUIDs fabricated between a conventional superconductor and single edge faces or corners of the Sr$_{2}$RuO$_{4 }$crystal.