Thermal algebraic-decay charge liquid driven by competing short-range Coulomb repulsion

TL;DR

This paper investigates a critical phase in a 2D extended Hubbard model where charge correlations decay algebraically, suggesting a Berezinskii-Kosterlitz-Thouless-like transition driven by competing Coulomb interactions.

Contribution

It demonstrates the existence of a critical phase with algebraic charge correlations in a 2D extended Hubbard model, linking it to the 2D XY universality class with $ ext{Z}_6$ anisotropy.

Findings

Identification of a Berezinskii-Kosterlitz-Thouless-like critical phase

Charge correlations decay algebraically in the intermediate temperature regime

Universality class of the critical phase is 2D XY with Z6 anisotropy

Abstract

We explore the possibility of a Berezinskii-Kosterlitz-Thouless-like critical phase for the charge degrees of freedom in the intermediate-temperature regime between the charge-ordered and disordered phases in two-dimensional systems with competing short-range Coulomb repulsion. As the simplest example, we investigate the extended Hubbard model with on-site and nearest-neighbor Coulomb interactions on a triangular lattice at half filling in the atomic limit by using a classical Monte Carlo method, and find a critical phase, characterized by algebraic decay of the charge correlation function, belonging to the universality class of the two-dimensional XY model with a $\mathbb{Z}_6$ anisotropy. Based on the results, we discuss possible conditions for the critical phase in materials.