Probing the chiral domain structure and dynamics in strontium ruthenate with nanoscale Josephson junctions

Previous work on Sr2RuO4 has shown that the superconducting state is unconventional with an order parameter symmetry of p x ± ipy. Measurements using Josephson Interferometry have shown evidence for chiral order parameter domains on the order of 1 μm in size. To further search for signatures of these domains we have fabricated Josephson junctions on clean Sr2RuO 4 single crystals (Tc=1.5 K) ranging from 500 nm to 4 μm wide. Using an applied magnetic field, we modulated the critical current of the junctions to make phase-sensitive measurements of the order parameter of the p-wave superconductor. We observed critical current characteristics consistent with single and multiple domains being present in the junctions. We also observed hysteresis effects in the junctions similar to previous experimental and theoretical work. We explored field cooling effects in the junctions that showed possible domain wall movement along the face of the junction. We also observed switches in the critical current that are not described currently by known theory and could be an indication of vertically oriented domains. We found that our smallest (500 nm) junctions consistently showed characteristics consistent with single domain junctions and that our results are consistent with 1 μm domains.