Superconducting energy gap and pairing interaction in high T/sub c/ oxides

The authors propose two characteristic features in high T/sub c/ oxides, La-Sr-Cu-O and Y-Ba-Cu-O: (i) the apparent discrepancy of the superconducting energy gap between far-infrared and quasi-particle tunneling measurements can be an indication of anisotropic Cooper pairing with spin singlet; (ii) the Coulomb interaction induces spin wave mode with the wave number of the Brillouin zone boundary and the energy close to 2Δ0, Δ0 being the maximum value of the superconducting energy gap. This mode may be observed by neutron inelastic scattering and tunneling experiments