Noncollinear and noncoplanar magnetic order in the extended Hubbard model on anisotropic triangular lattice

TL;DR

This study explores the phase diagram of the extended Hubbard model on an anisotropic triangular lattice, revealing diverse non-collinear and non-coplanar magnetic phases and their relation to charge order, relevant for layered triangular materials.

Contribution

It introduces a mean-field approach that treats various magnetic phases equally and uncovers new spin-charge ordered states in the extended Hubbard model.

Findings

Identification of stable non-collinear and non-coplanar magnetic phases.

Discovery of charge-ordered states at specific fillings.

Revelation of unconventional spin-charge orderings in a simple model.

Abstract

Motivated by the importance of non-collinear and non-coplanar magnetic phases in determining various electrical properties of magnetic materials, we investigate the phase diagrams of the extended Hubbard model on anisotropic triangular lattice. We make use of a mean-field scheme that treats collinear, non-collinear and non-coplanar phases on equal footing. In addition to the ferromagnetic and 120{\deg} antiferromagnetic phases, we find the four-sublattice flux, the 3Q non-coplanar and the non-collinear charge-ordered states to be stable at specific values of filling fraction $n$. Inter-site Coulomb repulsion leads to intriguing spin-charge ordered phases. Most notable of these are the collinear and non-collinear magnetic states at $n=2/3$, which occur together with a pinball-liquid-like charge order. Our results demonstrate that the elementary single-orbital extended Hubbard model on a triangular lattice hosts unconventional spin-charge ordered phases, which have been reported in more complex and material-specific electronic Hamiltonians relevant to layered triangular systems.