Anomalously strong small-q electron-phonon coupling in cuprates due to dielectricity

We consider the role of the enormous ionic dielectric constant epsilon(0) approximate to 30-50 in the cuprates. The ionically-screened Thomas-Fermi screening parameter (q) over tilde(TF) = [4 pi e(2)N(E-F)/epsilon(0)](1/2) is extremely small, namely 0.2-0.3 Angstrom(-1). The elect;on-phonon coupling constant I(q, omega) is found to be anomalously large for q approximate to (q) over tilde(TF) and small omega, accounting for the CDW observed in overdoped BSCCO with wavevector 0.24 Angstrom(-1). Using the Eliashberg theory we derive from this I(q, omega) a maximum T-c of abcut 200 K. The small electron-phonon scattering angle Delta Theta = (q) over tilde(TF)k(F approximate to 0.3) rad acounts for the observed d-wave pairing, as originating from a phonon-mediated mechananism.