Diversity of charge orderings in correlated systems

TL;DR

This paper investigates the charge ordering phenomena in a simplified extended Hubbard model, deriving exact ground state diagrams and analyzing how finite temperatures influence degeneracies and phase transitions.

Contribution

It provides exact ground state diagrams for the model across different dimensions and explores temperature effects on degeneracy removal and phase emergence.

Findings

Exact ground state diagrams for various lattice dimensions.

Finite temperature removes degeneracies in the ground state.

Identification of critical interactions for new ordered phases.

Abstract

The phenomenon associated with inhomogeneous distribution of electron density is known as a charge ordering. In this work, we study the zero-bandwidth limit of the extended Hubbard model, which can be considered as a simple effective model of charge ordered insulators. It consists of the on-site interaction $U$ and the intersite density-density interactions $W_1$ and $W_2$ between nearest-neighbors and next-nearest neighbors, respectively. We derived the exact ground state diagrams for different lattice dimensionalities and discuss effects of small finite temperatures in the limit of high dimensions. In particular, we estimated the critical interactions for which new ordered phases emerge (laminar or stripe and four-sublattice-type). Our analysis show that the ground state of the model is highly degenerated. One of the most intriguing finding is that the nonzero temperature removes these degenerations.