IMPORTANCE OF LONG-RANGE ELECTRON-PHONON COUPLING IN HIGH-TC SUPERCONDUCTORS

It is shown that the long-range part of the electron-phonon coupling (rigidly displaced ionic potentials screened by a background dielectric constant ε∞ and by holes moving along the CuO2 planes) is large in YBa2Cu3O7 due to imperfect screening. Using a simple phenomenological model for the phonon part the long-range contribution to the Eliashberg function α2F(ω) is evaluated yielding a value of about 2.4 for λ. The calculation suggests that this long-range part which is neglegible in usual metals plays an important role in high-Tc oxides. © 1990 Springer-Verlag.