The 3d-to-4s-by-2p highway to superconductivity in cuprates

TL;DR

This paper proposes that a conventional intra-atomic s-d two-electron exchange interaction within copper atoms explains the high critical temperature and d_{x^2-y^2} symmetry in cuprate superconductors, offering a new perspective on their mechanism.

Contribution

It introduces a forgotten intra-atomic s-d exchange as a key pairing interaction, providing a conventional explanation for high-temperature superconductivity in cuprates.

Findings

The intra-atomic s-d exchange is a strong (~eV) pairing interaction.

BCS theory with this interaction explains experimental observations.

Predicts the d_{x^2-y^2} symmetry of the superconducting gap.

Abstract

High-temperature superconductors are nowadays found in great variety and hold technological promise. It is still an unsolved mystery that the critical temperature T_c of the basic cuprates is so high. The answer might well be hidden in a conventional corner of theoretical physics, overlooked in the recent hunt for exotic explanations of new effects in these materials. A forgotten intra-atomic s-d two-electron exchange in the Cu atom is found to provide a strong (~eV) electron pairing interaction. A Bardeen-Cooper-Schrieffer approach can explain the main experimental observations and predict the correct d_{x^2-y^2} symmetry of the gap.