Slave fermion approach to the metallic phase in large $U_d$ high-T$_c$ cuprates

TL;DR

This paper develops a slave fermion approach to study the metallic phase in high-Tc cuprates with large on-site Coulomb repulsion, revealing moderate effective interactions and their impact on magnetic correlations.

Contribution

It formulates a time-dependent perturbation theory in the infinite U limit for the three-band Emery model, highlighting local gauge invariance and charge transfer effects.

Findings

Band narrowing and charge transfer disorder observed

Effective oxygen-site repulsion is moderate

Enhanced incommensurate SDW correlations

Abstract

Atomic repulsion $U_d$ on the Cu site in high T$_c$ cuprates is large but, surprisingly, some important properties are consistent with moderate couplings. The time dependent perturbation theory with slave particles is therefore formulated in the $U_d\to\infty$ limit for the metallic phase in the physically relevant regime of the three-band Emery model. The basic theory possesses the local gauge invariance asymptotically but its convergence is fast when the average occupation of the Cu-site is small. The leading orders exhibit the band narrowing and the dynamic Cu/O$_2$ charge transfer disorder. The effective local repulsion between particles on oxygen sites is shown to be moderate in the physical regime under consideration. It enhances the coherent incommensurate SDW correlations. The latter compete with the Cu/O$_2$ charge transfer disorder, in agreement with basic observations in high T$_c$ cuprates.