The unconventional superconductivity of Sr2RuO4

We review the evidence for unconventional superconductivity in Sr2RuO4; the pairing in this material is certainly non-s-wave, and most of the current observations can be accounted for by a particular p-wave state, which is do ubly degenerate and breaks time-reversal symmetry. Our observations of the flux lattice by small-angle neutron scattering contribute to this picture. The square flux: lattice and the intensity of the diffracted signal indicat e that superconductivity resides primarily on the gamma sheet of the Fermi surface, which is derived from the Ru - d(xy) orbitals. This is in agreemen t with the "orbital-dependent" p-wave scenario. Furthermore, the shape of t he flux lines derived from these measurements is strongly indicative of a t wo-component order parameter.