Unusual low-temperature behavior in the half-filled band of the one-dimensional extended Hubbard model in atomic limit

TL;DR

This paper investigates the low-temperature anomalous behavior in the half-filled band of a one-dimensional extended Hubbard model in the atomic limit, revealing pseudo-transition features that mimic phase transitions without actual finite-temperature phase change.

Contribution

The study provides a rigorous analysis of the low-temperature behavior of the extended Hubbard model, identifying and characterizing pseudo-transitions and anomalous phenomena in the half-filled band.

Findings

Identification of pseudo-transition between AP and PM phases

Anomalous behavior mimicking first- and second-order transitions

No true finite-temperature phase transition occurs

Abstract

Recently, a kind of finite-temperature pseudo-transition was observed in several quasi-one-dimensional models. In this work, we consider a genuine one-dimensional extended Hubbard model in the atomic limit, influenced by an external magnetic field and with the arbitrary number of particles controlled by the chemical potential. The one-dimensional extended Hubbard model in the atomic limit was initially studied in the seventies and has been investigated over the past decades, but it still surprises us today with its fascinating properties. We rigorously analyze its low-temperature behavior using the transfer matrix technique and provide accurate numerical results. Our analysis confirms that there is an anomalous behavior in the half-filled band, specifically occurring between the alternating pair (AP) and paramagnetic (PM) phases at zero temperature. Previous investigations did not deeply identify this anomalous behavior, maybe due to the numerical simplicity of the model, but from analytical point of view this is not so easy to manipulate algebraically because one needs to solve an algebraic cubic equation. In this study, we explore this behavior and clearly distinguish the pseudo-transition, which could easily be mistaken with a real phase transition. This anomalous behavior mimics features of both first- and second-order phase transitions. However, due to its nature, we cannot expect a finite-temperature phase transition in this model.