Magnon Decay in Noncollinear Quantum Antiferromagnets

TL;DR

This paper investigates the spontaneous two-magnon decay processes in noncollinear Heisenberg antiferromagnets, focusing on a spin-1/2 triangular lattice model and analyzing how kinematic conditions influence the excitation spectrum.

Contribution

It provides a detailed analysis of magnon decay mechanisms in noncollinear quantum antiferromagnets using the 1/S-approximation, highlighting the importance of kinematic conditions.

Findings

Kinematic conditions are crucial for magnon decay existence.

Spectrum features depend on wave-length and model parameters.

Higher-order corrections and model generalizations are discussed.

Abstract

Instability of the excitation spectrum of an ordered noncollinear Heisenberg antiferromagnet (AF) with respect to spontaneous two-magnon decays is investigated. We use a spin-1/2 AF on a triangular lattice as an example and examine the characteristic long- and short wave-length features of its zero-temperature spectrum within the 1/S-approximation. The kinematic conditions are shown to be crucial for the existence of decays and for overall properties of the spectrum. The XXZ and the J-J' generalizations of the model, as well as the role of higher-order corrections are discussed.