Off-site repulsion-induced triplet pairing: DCA and FLEX study for Sr ₂RuO₄

To shed new light on the mechanism of the triplet superconductivity in Sr2RuO4, we have studied how the introduction of the off-site Coulomb repulsion (V), which should enhance charge fluctuations, affects the pairing symmetry. We find, with the dynamical cluster approximation combined with the quantum Monte Carlo method and the fluctuation exchange approximation, that, while dx2-y2-pairing dominates over p in the absence of V, introduction of V favours px+y and dxy pairs that are formed across second-neighbour sites, while dx2-y2,px across nearest-neighbours are suppressed. The degenerate px±y should form a chiral px+y+ipx-y, which has nodes around (±π,0) and (0,±π) that is consistent with a recent measurement of the specific heat in rotating magnetic fields. So the present result, also confirmed with the fluctuation exchange approximation, provides an example where the off-site repulsion plays an essential role in the triplet superconductivity.