Slave-boson based configuration-interaction approach for the Hubbard model

TL;DR

This paper introduces a slave-boson based configuration-interaction method to enhance energy calculations for the Hubbard model, comparing it with Hartree-Fock and Gutzwiller approaches, revealing limitations in the thermodynamic limit.

Contribution

It develops a novel CI approach within the slave-boson framework for the Hubbard model, improving energy estimates for symmetry-broken states.

Findings

CI improves energy estimates over saddle-point solutions

Comparison shows differences with Hartree-Fock results

CI does not improve variational results in the thermodynamic limit

Abstract

Based on the Kotliar-Ruckenstein slave-boson scheme we develop a configuration-interaction (CI) approach which is suitable to improve the energy of symmetry-broken saddle-point solutions. The theory is applied to spin-polaron states in the Hubbard model and compared with analogous results obtained within the Hartree-Fock approximation. In addition we show that within the infinite ${\cal D}$ prescription of the Gutzwiller method a CI approach does not improve the variational result since in the thermodynamic limit matrix elements between different inhomogeneous states vanish due to an 'orthogonality catastrophe'.