Electronic correlations in the Hubbard model on a bi-partite lattice

TL;DR

This paper uses the coupled-cluster method to analyze electronic correlations in the Hubbard model on bipartite lattices, reproducing known results in 1D and exploring properties in 2D materials.

Contribution

It demonstrates the application of the coupled-cluster method to the Hubbard model on bipartite lattices, including reproducing the zero order parameter in 1D and analyzing 2D lattice excitations.

Findings

Reproduces zero order parameter in 1D Hubbard model

Analyzes charge and spin excitations in 2D models

Shows the importance of critical correlations in CCM coefficients

Abstract

In this work we study the Hubbard model on a bi-partite lattice using the coupled-cluster method (CCM). We first investigate what, within this approach, allows us to reproduce the zero order parameter in the 1D model, as predicted by the exact solution. We show that we need a critical correlation in some of the coupled-cluster model coefficients to reproduce this result, as can be obtained by applying some very accurate results using the CCM for the Heisenberg model. Using the same approach we then tackle the 2D Hubbard model on a square and a honeycomb lattice, both of which can be thought to represent 2D materials. We also analyse the charge and spin excitations, with reasonable results.