Unconventional superconductivity in Sr2RuO4

We have performed ZF-μSR measurements of Sr2RuO4 and have observed a spontaneous magnetic field below Tc. This observation, combined with other symmetry considerations demonstrates that superconductivity in Sr2RuO4 is of ‘p-wave’ (odd-parity) type. Our transverse field μSR measurements in the mixed state with B=150G||ĉ clearly indicate the presence of a square flux lattice. We have analysed the field distribution in terms of the penetration depth, coherence length and a Fermi surface anisotropy term and found λ(T=0)=1900Å. λ(T→0) is quite flat, consistent with a superconducting gap with no nodes as expected for the Eu(kx±iky) state.