Spin-gap phase in nearly-half-filled one-dimensional conductors coupled with phonons

TL;DR

This paper investigates the complex interplay between spin, charge, and phonons in nearly-half-filled one-dimensional conductors, revealing various phases including a metallic phase with a spin gap influenced by electron-phonon interactions.

Contribution

It introduces a renormalization group analysis showing how electron-phonon coupling affects phase transitions and spin-charge correlations in one-dimensional conductors.

Findings

Identification of a metallic phase with a spin gap near half filling

Demonstration of phonon-assisted backward scatterings influencing the spin gap

Discovery of phase variations depending on energy scale relations

Abstract

Asymptotic properties of nearly-half-filled one-dimensional conductors coupled with phonons are studied through a renormalization group method. Due to spin-charge coupling via electron-phonon interaction, the spin correlation varies with filling as well as the charge correlation. Depending on the relation between cut-off energy scales of the Umklapp process and of the electron-phonon interaction, various phases appear. We found a metallic phase with a spin gap and a dominant charge- density-wave correlation near half filling between a gapless density-wave phase (like in the doped repulsive Hubbard model) and a superconductor phase with a spin gap. The spin gap is produced by phonon-assisted backward scatterings which are interfered with the Umklapp process constructively or destructively depending on the character of electron-phonon coupling.