Spin nematic state for a spin S=3/2 isotropic non-Heisenberg magnet

TL;DR

This paper investigates the complex spin nematic phases in an isotropic S=3/2 magnet, revealing unique symmetry breakings including time-reversal symmetry, using a mean-field theoretical approach.

Contribution

It introduces a detailed mean-field analysis of spin nematic states in an S=3/2 system, highlighting novel symmetry properties and the role of quantum averages cubic over spin components.

Findings

Identification of two distinct spin nematic phases with complex symmetry breaking.

Description of the order parameters involving vector-director and pseudospin vectors.

Analysis of the relationship between nematic and antinematic phases through pseudospin configurations.

Abstract

$S=3/2$ system with general isotropic nearest-neighbor exchange within a mean-field approximation possesses a magnetically ordered ferromagnetic state and antiferromagnetic state, and two different spin nematic states, with zero spin expectation values. Both spin nematic phases display complicated symmetry break, including standard rotational break described by the vector-director $\vec {u}$ and specific symmetry break with respect to the time reversal. The break of time reversal is determined by non-trivial quantum averages cubic over the spin components and can be described by unit "pseudospin" vector $\vec {\sigma}$. The vectors $\vec {\sigma}$ on different sites are parallel for a nematic state, and $\vec {\sigma}$'s are antiparallel for different sublattices for an antinematic phase.