%0 Journal Article
%T The Isotope Effect in d-Wave Superconductors
%A H. -B. Sch¨ąttler
%A C. -H. Pao
%J Physics
%D 1995
%I arXiv
%R 10.1103/PhysRevLett.75.4504
%X Based on recently proposed anti-ferromagnetic spin fluctuation exchange models for $d_{x^2-y^2}$-superconductors, we show that coupling to harmonic phonons {\it{cannot}} account for the observed isotope effect in the cuprate high-$T_c$ materials, whereas coupling to strongly anharmonic multiple-well lattice tunneling modes {\it{can}}. Our results thus point towards a strongly enhanced {\it{effective}} electron-phonon coupling and a possible break-down of Migdal-Eliashberg theory in the cuprates.
%U http://arxiv.org/abs/cond-mat/9511086v1