Odd-parity superconductivity in Sr₂RuO₄

Phase-sensitive measurements were made on Sr₂RuO₄ to establish unambiguously the odd-parity pairing in this material. The critical current of Au_0.5In_0.5-Sr₂RuO₄ superconducting quantum interference devices prepared on Sr₂RuO 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 ₂RuO₄ changes by π under inversion. This result verifies the odd-parity pairing symmetry and the formation of spin-triplet Cooper pairs in Sr₂RuO₄.