Electron-phonon interaction in the cuprates: Breathing versus buckling mode

Using a cell perturbation method, we investigate the role played by two imp ortant phonon modes in high-temperature superconductors, namely, the in-pla ne-oxygen breathing and buckling modes. We demonstrate that diagonal electr on-phonon interactions, present in both modes, lead to opposite interaction s: attraction for the buckling and repulsion for the breathing mode. When t he nondiagonal electron-phonon interaction is included with the breathing m ode, the possibility of attraction also arises within this mode. We also sh ow that the effective Hamiltonian may be reduced to a Hubbard-like model wi th a simple, renormalized electron-phonon interaction. [S0163-1829(99)14121 -3].