Mean-Field Analysis of Electric Field Effect on Charge Orders in Organic Conductors

TL;DR

This paper develops a nonequilibrium Green's function approach to analyze how electric fields influence charge ordering in organic conductors, revealing that electric fields stabilize certain charge order states.

Contribution

The study introduces a static nonequilibrium Hartree approximation method based on Keldysh Green's functions to analyze charge order stability under electric fields.

Findings

Electric field stabilizes 3-fold charge order.

Amplitude of 3-fold order decreases with electric field.

Horizontal order amplitude remains unchanged.

Abstract

In order to investigate charge ordering phenomena under electric field, static nonequilibrium Hartree approximation (SNHA) method is formulated on the basis of the nonequilibrium Green's functions introduced by Keldysh. By applying the SNHA to the 3/4-filling extended Hubbard model on anisotropic triangular lattice, we study the stabilities and amplitudes of 3-fold and horizontal charge orders in ${\theta}$ and ${\theta}_d$-(BEDT-TTF)$_2X$ salts under the electric field. The obtained results show that the electric field stabilizes the 3-fold state in comparison to the horizontal state. The amplitude of the 3-fold state tends to decrease by the field, whereas that of the horizontal state does not change.