Doped AB_2 Hubbard Chain: Spiral, Nagaoka and RVB States, Phase Separation and Luttinger Liquid Behavior

TL;DR

This study explores the doped AB₂ Hubbard chain, revealing diverse phases including spiral, ferromagnetic, phase separation, RVB states, and Luttinger liquid behavior through extensive numerical analysis.

Contribution

It provides a comprehensive numerical analysis of the doped AB₂ Hubbard chain, highlighting new phase behaviors and transitions across different doping levels and interaction regimes.

Findings

Spiral states near half-filling in weak coupling

Nagaoka ferromagnetism in the infinite-U limit

Phase separation and RVB states at higher doping

Abstract

We present an extensive numerical study of the Hubbard model on the doped AB$_2$ chain, both in the weak coupling and the infinite-U limit. Due to the special unit cell topology, this system displays a rich variety of phases as function of hole doping ($\delta$) away from half-filling. Near half-filling, spiral states develop in the weak coupling regime, while Nagaoka itinerant ferromagnetism is observed in the infinite-U limit. For higher doping the system phase-separates before reaching a Mott insulating phase of short-range RVB states at $\delta=1/3$. Moreover, for $\delta>1/3$ we observe a crossover, which anticipates the Luttinger liquid behavior for $\delta > 2/3$.