PUB - Publikationen an der Universität Bielefeld

A phenomenological spin-fluctuation analysis [Dahm et al., Nat. Phys. 5, 217 (2009)], based upon inelastic neutron scattering (INS) and angular resolved photoemission spectroscopy (ARPES) data for YBCO6.6 (T-c = 61 K), is used to calculate the functional derivative of the d-wave eigenvalue lambda(d) of the linearized gap equation with respect to the imaginary part of the spin susceptibility. chi '' (q,omega) at 70K. For temperatures near T-c, the variation of T-c with respect to. chi '' (q,omega) is proportional to this functional derivative. We find that above an energy similar to 4T(c) the functional derivative becomes positive so that adding spin-fluctuation spectral weight at higher frequencies leads to an increase in T-c. The strongest pairing occurs for large momentum transfers, and small momentum spin-fluctuations suppress the pairing.