New Comparisons for Local Quantities of the Two-Dimensional Hubbard Model

TL;DR

This paper evaluates the composite operator method for the 2D Hubbard model by comparing its predictions for double occupancy and internal energy with numerical results, demonstrating high accuracy.

Contribution

It introduces and validates the composite operator method as a reliable approximation for key properties of the 2D Hubbard model.

Findings

Excellent agreement with Lanczos and quantum Monte Carlo data

Reliable approximation at half-filling and away from it

Supports use of the composite operator method for similar models

Abstract

We have compared the results of our approximation scheme, the composite operator method, for the double occupancy and the internal energy of the two-dimensional Hubbard model with numerical data obtained by means of the Lanczos and quantum Monte Carlo schemes. The agreement is very good at both half-filling and away from it showing how reliable is the approximation scheme.