Screened superexchange mechanism for superconductivity applied to cuprates

TL;DR

This paper introduces a superexchange-based screening mechanism for superconductivity in cuprates, using a formalism that predicts phase diagrams and spectra consistent with experimental data.

Contribution

It adapts the Kohn-Luttinger superexchange formalism to cuprates, deriving predictions for phase diagrams and spectra using ab initio data and a Schrieffer-Wolff transformation.

Findings

Predicted phase diagram matches experimental observations.

Derived doping-dependent band energies consistent with data.

Identified superexchange as a key mechanism for pairing in cuprates.

Abstract

In 1965, Kohn and Luttinger published a note revealing that dynamical screening of the repulsive Coulomb interaction leads under certain conditions to an effective attraction necessary for the formation of Cooper pairs. We propose such a formalism adapted to the cuprates where the screening arises from the superexchange dynamics of virtual holes in the oxygen orbitals of the $Cu O_2$ plane. Using an adequate Schrieffer-Wolff transformation, the basic Hartree-Fock-Bogoliubov (HFB) method and the {\it ab initio} data on orbitals (energy, hopping, interaction), we derive some predictions for the temperature-doping phase diagram (pseudo-gap, strange metal, antiferromagnetism, superconducting and normal states) and for the doping dependant band energy spectrum in semi-quantitative agreement with observations.