Low-energy states for correlated-electron models in the strong-coupling limit

TL;DR

This paper investigates exactly solvable models of strongly correlated electrons with infinite on-site repulsion, constructing approximate states that help estimate ground-state energies and analyzing their properties in the thermodynamic limit.

Contribution

It introduces a tractable (2N-1)-particle state for these models that approximates the ground state and provides a method to calculate variational bounds on the ground-state energy.

Findings

Constructed a (2N-1)-particle state that becomes degenerate with the ground state asymptotically.

Provided analytical bounds for the Hubbard chain with three sites per unit cell.

Compared variational bounds with numerically exact results, validating the approach.

Abstract

We study a class of exactly solvable models for strongly correlated electrons, defined on a set of N cells, and with infinite on-site repulsion on part of the sites of each cell. For 2N or more electrons the exact ground state is known. We construct a tractable (2N-1)-particle state which becomes asymptotically degenerate to the ground state in the thermodynamic limit for one special D-dimensional model. For other models, that state may be used to calculate variational upper bounds on the ground-state energy. For a Hubbard chain with three sites per unit cell, the analytical bound is compared to numerically exact results.