Exact Ground State of Strongly Correlated Electron Systems from Symmetry-Entangled Wave-Functions

TL;DR

This paper demonstrates that the exact ground state of a four-site Hubbard model can be obtained using symmetry-entangled wave-functions, outperforming traditional Gutzwiller approaches across all interaction strengths.

Contribution

It introduces a symmetry-projected Slater determinant method that exactly reproduces the ground state of a strongly correlated electron system.

Findings

Exact ground state recovered by symmetry projection

Outperforms Gutzwiller wave-function at all interaction strengths

Applicable to small Hubbard models

Abstract

The four-site Hubbard model is considered from the exact diagonalisation and variational method points of view. It is shown that the exact ground-state can be recovered by a symmetry projected Slater determinant, irrespective of the interaction strength. This is in contrast to the Gutzwiller wave-function, which is calculated as well.