Edge Josephson Junction Detection of Topological Chiral Edge Current in Spin-triplet Superconductor Sr₂RuO₄ with a Calibrated Sensitivity

Sr₂RuO₄ is an unconventional superconductor predicted to have a spin-triplet, p-wave order parameter, however a full description of the order parameter has yet to be resolved experimentally despite two decades of research. Phase-sensitive measurements using AuIn-Sr₂RuO₄ SQUIDs on bulk crystals, first performed over a decade ago, clearly demonstrated that the order parameter has an odd parity, making the so called Γ₅, the chiral p-wave pairing state the most likely candidate. We have fabricated Josephson junctions between Al and the edges of thin (<1 μm) crystal plates of Sr₂RuO₄ to determine the precise pairing symmetry in the few-domain regime. We compare our results on flake corner junctions to those of bulk measurements, where neither a minimum nor maximum was observed at zero field in the I_c-H interference pattern. We also use junctions fabricated on single faces of the crystal to probe the existence of the predicted chiral edge currents. It is found that a non-zero remnant magnetic field exists within the Sr₂RuO₄ samples below T_c, even when subject to zero-field cooling. Together these results reaffirm that Sr₂RuO₄ has an odd-parity pairing symmetry, and provides strong support to the possibility of chiral p-wave, topological superconductivity in this material.