Finite-Temperature Charge-Ordering Transition and Fluctuation Effects in Quasi-One-Dimensional Electron Systems at Quarter Filling

TL;DR

This paper theoretically investigates finite-temperature charge-ordering transitions in quasi-1D molecular conductors, revealing how interchain Coulomb interactions and 1D fluctuations influence the transition across different coupling regimes.

Contribution

It introduces a comprehensive analysis combining mean-field and bosonization techniques to describe charge-ordering transitions at finite temperature in quasi-1D systems.

Findings

Transition temperature depends on interchain Coulomb repulsion $V_ot$.

Three distinct regimes identified based on coupling strength.

Analytical formulas derived for $V_ot$ dependence of transition temperature.

Abstract

Finite-temperature charge-ordering phase transition in quasi one-dimensional (1D) molecular conductors is investigated theoretically, based on a quasi 1D extended Hubbard model at quarter filling with interchain Coulomb repulsion $V_\perp$. The interchain term is treated within mean-field approximation whereas the 1D fluctuations in the chains are fully taken into account by the bosonization theory. Three regions are found depending on how the charge ordered state appears at finite temperature when $V_\perp$ is introduced: (i) weak-coupling region where the system transforms from a metal to a charge ordered insulator with finite transition temperature at a finite critical value of $V_\perp$, (ii) an intermediate region where this transition occurs by infinitesimal $V_\perp$ due to the stability of inherent 1D fluctuation, and (iii) strong-coupling region where the charge ordered state is realized already in the purely 1D case, of which the transition temperature becomes finite with infinitesimal $V_\perp$. Analytical formula for the $V_\perp$ dependence of the transition temperature is derived for each region.