Phase separation in the one-dimensional Hubbard model

TL;DR

This paper investigates the phase diagram of the one-dimensional Hubbard model, revealing phase separation phenomena near specific fillings and analyzing the stability of various magnetic phases in the system.

Contribution

The study extends previous Hartree-Fock analyses by mapping the phase diagram in the $U$ plane, identifying phase separation regions and the instability of spiral phases.

Findings

Spiral phase is unstable against phase separation near certain fillings.

Large $U$ induces phase separation at specific doping levels.

The phase diagram includes antiferromagnetism, ferromagnetism, and spin density waves.

Abstract

The Hartree-Fock ground-state phase diagram of the one-dimensional Hubbard model is calculated in the $\mu-U$ plane, restricted to phases with no charge density modulation, extending the results presented in cond-mat/9511116. This allows antiferromagnetism, saturated ferromagnetism, spiral spin density waves and a collinear structure with unit cell $\uparrow \uparrow \downarrow \downarrow$. The spiral phase is unstable against phase separation near quarter-, half- and three-quarter-filling. For large $U$ this occurs at hole (or electron) doping of $(3t/\pi^{2}U)^{1/3}$ from half filling.