Correlation between T_c and the Cu 4s level reveals the mechanism of high-temperature superconductivity

TL;DR

This paper links the critical temperature of high-T_c cuprate superconductors to the copper 4s level position, explaining the mechanism through a four-band model and intra-atomic exchange within BCS theory, potentially solving a long-standing puzzle.

Contribution

It introduces a comprehensive four-band model incorporating Cu 3d, Cu 4s, and O 2p orbitals, explaining T_c dependence via the Cu 4s level within the BCS framework, offering a new understanding of high-T_c superconductivity.

Findings

T_c correlates with the Cu 4s level position.

The four-band model explains T_c variation from 25 to 125 K.

Intra-atomic exchange in Cu 3d--Cu 4s interactions is key.

Abstract

Band structure trends in hole-doped cuprates and correlations with T_c are interpreted within the s--d exchange mechanism of high-T_c superconductivity. The dependence of T_c on the position of the copper 4s level finds a natural explanation in the generic Cu 3d, Cu 4s, O 2p_x and O 2p_y four-band model. The Cu 3d--Cu 4s intra-atomic exchange interaction is incorporated in the standard BCS scheme. This dependence of T_c in the whole interval of 25--125 K has no alternative explanation at present, and possibly this quarter of a century standing puzzle is already solved.