Effect of dopant atoms on local superexchange in cuprate superconductors: a perturbative treatment

TL;DR

This paper investigates how dopant atoms affect local superexchange interactions in cuprate superconductors using a perturbative approach within the three-band Hubbard model, revealing sign changes dependent on dopant-induced atomic level variations.

Contribution

It introduces a perturbative calculation of local superexchange in cuprates considering dopants within the three-band Hubbard model, highlighting differences from one-band models.

Findings

Sign of superexchange change depends on dopant-induced atomic level variations.

Contrasts with one-band Hubbard model results.

Relevance for pairing mechanism theories in cuprates.

Abstract

Recent scanning tunneling spectroscopy experiments have provided evidence that dopant impurities in high- Tc superconductors can strongly modify the electronic structure of the CuO2 planes nearby, and possibly influence the pairing. To investigate this connection, we calculate the local magnetic superexchange J between Cu ions in the presence of dopants within the framework of the three-band Hubbard model, up to fifth-order in perturbation theory. We demonstrate that the sign of the change in J depends on the relative dopant-induced spatial variation of the atomic levels in the CuO2 plane, contrary to results obtained within the one-band Hubbard model. We discuss some realistic cases and their relevance for theories of the pairing mechanism in the cuprates