Evaluation of the electron-phonon interaction and transition temperature in the oxide superconductors

Abstract

The Allen-Dynes equation applicable to the oxide superconductors is studied, which shows that for moderate values of the electron-phonon coupling constant the superconducting transition temperature is found in the range of 100 K. This result is based on an approximate evaluation of large values of the McMillan-Hopfield parameter and evidence from frozen-phonon calculations that strong ionic character in the copper oxide superconductors invalidates the rigid muffintin approximation.