The extended Hubbard model with attractive interactions

TL;DR

This paper compares extended dynamical mean-field theory and dual boson methods in analyzing the phase diagram of the extended Hubbard model with both attractive and repulsive interactions, highlighting their agreement and differences.

Contribution

It provides a comparative analysis of EDMFT and dual boson methods for the extended Hubbard model, emphasizing their agreement in the attractive regime and differences in the repulsive regime.

Findings

EDMFT and DB agree in the attractive V regime with phase separation.

Significant differences between EDMFT and DB in the repulsive V regime for checkerboard order.

The methods' agreement varies depending on the nature of interactions in the model.

Abstract

We discuss the phase diagram of the extended Hubbard model with both attractive and repulsive local and nonlocal interactions. The extended dynamical mean-field theory (EDMFT) and the dual boson method (DB) are compared. The latter contains additional nonlocal correlation effects that are not incorporated in EDMFT. We find that EDMFT and DB give almost identical results in the attractive $V$ regime, where phase separation occurs. This is quite a difference with the previously studied repulsive $V$ regime, where EDMFT and DB give very different phase boundaries for the checkerboard order phase, especially at small $U$.