Possible electronic properties in high-Tc superconducting cuprates from cluster calculations

Electronic structure calculations have been performed on a Ca2Cu4O4 cluster to model possible local properties of relevance to superconductivity in cuprates. Explicit account of near-degeneracies suggests the pairing potential mixes anisotropic s and d symmetries as a result of going beyond the independent particle description. Pairing results from the screening of cation repulsion across the CuO2 plane. Pair-breaking energies in the range 0–60 meV are computed dependent on the cation to plane distance. A possible mechanism for superconductivity emerges.