Spontaneous Magnon Decays

TL;DR

This paper reviews the phenomenon of spontaneous magnon decays in quantum antiferromagnets, discussing theoretical conditions, parallels with other excitations, and potential experimental observations in various magnetic systems.

Contribution

It provides a comprehensive theoretical overview of spontaneous magnon decays, including symmetry conditions, decay mechanisms, and comparisons with numerical data and experimental prospects.

Findings

Identification of symmetry and kinematic conditions for magnon decays

Analysis of three principal decay cases in different magnetic systems

Comparison of analytical results with numerical data and experimental implications

Abstract

A theoretical overview of the phenomenon of spontaneous magnon decays in quantum antiferromagnets is presented. The intrinsic zero-temperature damping of magnons in quantum spin systems is a fascinating many-body effect, which has recently attracted significant attention in view of its possible observation in neutron-scattering experiments. An introduction to the theory of magnon interactions and a discussion of necessary symmetry and kinematic conditions for spontaneous decays are provided. Various parallels with the decays of anharmonic phonons and excitations in superfluid 4He are extensively used. Three principal cases of spontaneous magnon decays are considered: field-induced decays in Heisenberg antiferromagnets, zero-field decays in spiral antiferromagnets, and triplon decays in quantum-disordered magnets. Analytical results are compared with available numerical data and prospective materials for experimental observation of the decay-related effects are briefly discussed.