Extending SQUID interferometry beyond the cuprates and beyond d-wave symmetry

Abstract

Phase-sensitive superconducting quantum interference device (SQUID) interferometry measurements have been instrumental in establishing the d-wave pairing symmetry of the high-temperature cuprates. We are now applying this approach to try to determine the symmetry of other superconducting materials suspected to be unconventional, such as the heavy fermion, organic, and ruthenate superconductors. We are also using modifications of the technique to probe details of the pairing state, such as the angular anisotropy of the order parameter magnitude and phase, the dependence of symmetry-induced spontaneous currents on sample geometry, and the onset of subdominant order parameter symmetries at interfaces and defects.