BOSON MEDIATORS OF HIGH-T-C SUPERCONDUCTIVITY - PHONONS VERSUS COMPOSITE BOSONS FROM THE SUPERCONDUCTING PHENOMENOLOGY

We address the question of whether boson mediators of high-T-c superco nductivity are composite (electronic) or independent phonons. For s-wa ve superconductivity we show from the available experiments that the h ypothesis of composite bosons is rather unlikely. Our analysis points naturally towards phonon mediators. In addition we point out that the eventual presence of a peak in the temperature dependence of the micro wave conductivity while the Hebel-Slichter peak is absent in the tempe rature dependence of the NMR relaxation rate can be understood within a phonon mechanism if one takes into account the modulation of the ele ctron-phonon coupling (predominance of forward scattering) induced by Coulomb correlation of the carriers.