Aligning chiral order parameter domains in Sr2RuO4: Josephson interferometry measurements

There is compelling evidence that the ruthenate superconductor Sr2RuO4 forms chiral order parameters of the form px+ipy and px-ipy. In zero magnetic field, these states are degenerate and result in the formation of a dynamical domain structure that has been detected by Josephson interferometry experiments [1]. However, the degeneracy between the order parameters can be lifted by applying a magnetic field while cooling the system through the superconducting transition. We present Josephson interferometry measurements on field-cooled Josephson junctions that show evidence for domain alignment, manifested by the enhancement of the critical current and qualitative changes of the critical current modulation pattern in applied magnetic field. We also report evidence for memory effects in the domain chirality. [1] Francoise Kidwingira \textit{et al}., \textit{Science}, October 26 2006 (10.1126/science.1133239).