Unusual ordered phases of highly frustrated magnets: a review

TL;DR

This review discusses the diverse ground states and excitations in highly frustrated quantum antiferromagnets, emphasizing novel collinear and nematic phases influenced by magnetic field, anisotropy, and spin size, with connections to experiments.

Contribution

It provides a comprehensive overview of the phase diagrams and novel magnetic states in frustrated antiferromagnets, highlighting effects of anisotropy, magnetic field, and quantum versus semiclassical regimes.

Findings

Identification of collinear spin density wave states

Discovery of spin nematic phases with gapped excitations

Analysis of phase diagrams across different spin magnitudes

Abstract

We review ground states and excitations of a quantum antiferromagnet on triangular and other frustrated lattices. We pay special attention to the combined effects of magnetic field h, spatial anisotropy R, and spin magnitude S. The focus of the review is on the novel collinear spin density wave and spin nematic states, which are characterized by fully gapped transverse spin excitations with $S^z = \pm 1$. We discuss extensively R-h phase diagram of the antiferromagnet, both in the large-S semiclassical limit and the quantum S=1/2 limit. When possible, we point out connections with experimental findings.