SPIN FLUCTUATIONS OF D-WAVE SUPERCONDUCTORS

The dynamic spin correlation function near the commensurate point Q = (pi,pi) in the superconducting state is calculated within mean field theory. We take the generalized t-J model as used by Tanamoto et al. For d-wave superconductor at T-0 K, we find that there will be no energy gap at incommensurate point, while the energy gap E(g) = 2 mu develops at commensurate point in the particle-hole channel. On the other hand for s-wave superconductor a large energy gap develops irrespective of the nature of antiferromagnetic fluctuations. Therefore the d-wave model describes the neutron scattering data from both La1.86Sr0.14CuO4 by Mason el al. and YBa2Cu3O6+x by Rossat-Mignod et al. quite well, while the s-wave model is incompatible with these results.