Odd-Parity Superconductivity in Sr 2 RuO 4

Abstract

Phase-sensitive measurements were made on Sr 2 RuO 4 to establish unambiguously the odd-parity pairing in this material. The critical current of Au 0.5 In 0.5 -Sr 2 RuO 4 superconducting quantum interference devices prepared on Sr 2 RuO 4 single crystals was found to be a maximum for devices with junctions on the same side of the crystal and a minimum for devices with junctions on opposite sides, in the limit of zero magnetic flux; these findings indicate that the phase of the superconducting order parameter in Sr 2 RuO 4 changes by π under inversion. This result verifies the odd-parity pairing symmetry and the formation of spin-triplet Cooper pairs in Sr 2 RuO 4 .