Mechanism of spin-triplet superconductivity in Sr2RuO4

The unique Fermi surfaces and their nesting properties of Sr2RuO4 are considered. The existence of unconventional superconductivity is demonstrated for the first time, by magnetic interactions (due to nesting) and phonon-mediated interactions. Two possible mechanisms of spin-triplet superconductivity are pointed out: one is due to the quasi-1D nature of the alpha and beta sheets of the Fermi surface and other is due to the anisotropy of antiferromagnetic (AF) fluctuations. The odd-parity superconductivity is favored in the alpha and beta sheets of the Fermi surface, and various superconductivities are possible in the gamma sheet. There area number of possible odd-parity gaps, which include the gaps with nodes, the breaking of time-reversal symmetry and d parallel to(z) over cap.