Repulsive Interactions Due to Breathing Modes in Ceramic High-Tc Superconductors

Abstract

What are examined are mutual interactions due to one-phonon exchanges of breathing modes of oxygen octahedrons in recently-discovered ceramic high- T c superconductors. Although mutual interactions due to breathing modes are attractive between the on-site pairs, as expected, they are repulsive between the nearest neighbors. On the basis of an argument that it is difficult for such on-site attractive interactions to overcome strong Coulomb repulsions because of narrow quasi-particle bands, the result obtained here implies that superconductivity should be realized by a certain non-phonon mechanism such as the nearest-neighbor superexchange interaction.