Exact results in a slave boson saddle point approach for a strongly correlated electron model

TL;DR

This paper demonstrates that the Kotliar-Ruckenstein slave boson saddle point method can accurately reproduce the exact solutions of a two-site strongly correlated electron model, including ground state and excitation levels.

Contribution

The authors introduce weight factors in the KR saddle point scheme, enabling exact agreement with known solutions for a simplified correlated electron model.

Findings

Ground state and excitation levels match exact diagonalization results.

Thermodynamics and correlation functions can be accurately obtained.

The approach validates the KR saddle point method for this model.

Abstract

We revisit the Kotliar-Ruckenstein (KR) slave boson saddle point evaluation for a two-site correlated electron model. As the model can be solved analytically, it is possible to compare the KR saddle point results to the exact many particle levels. The considered two site cluster mimics an infinite-$U$ single-impurity Anderson model with a nearest neighbor Coulomb interaction: one site is strongly correlated with an infinite local Coulomb repulsion which hybridizes with the second site, on which the local Coulomb repulsion vanishes. Making use of the flexibility of the representation we introduce appropriate weight factors in the KR saddle point scheme. Ground state and all excitation levels agree with the exact diagonalization results. Thermodynamics and correlation functions may be recovered in a suitably renormalized saddle point evaluation.