# Changes to the t-J Model From Inclusion of Two-Site Nearest-Neighbor Coulomb Interactions

## TL;DR

This paper investigates how including two-site nearest-neighbor Coulomb interactions modifies the t-J model, providing a more comprehensive understanding of strongly correlated electron systems beyond the traditional Hubbard model approximation.

## Contribution

It introduces a more complete model incorporating additional Coulomb interaction terms and analyzes their impact on the t-J model.

## Key findings

- Inclusion of nearest-neighbor Coulomb interactions alters the t-J model parameters.
- Neglected interaction terms significantly influence the physics of correlated electrons.
- The extended model offers a more accurate description of electron correlations in solids.

## Abstract

To date, the Hubbard model and its strong coupling limit, the t-J model, serve as the canonical model for strongly correlated electron systems in solids. Approximating the Coulomb interaction by only the on-site term (Hubbard U-term), however, may not be sufficient to describe the essential physics of interacting electron systems. We develop a more complete model in which all the next leading order terms besides the on-site term are retained. Moreover, we discuss how the inclusion of these neglected interaction terms in the Hubbard model changes the t-J model.