Magnon Localization in Mattis Glass

TL;DR

This paper investigates how magnons behave in disordered Mattis glass materials, revealing localization in 2D and delocalization with diffusive transport in 3D, and calculates the resulting finite thermal conductivity.

Contribution

It provides a detailed analysis of magnon localization and transport in Mattis glass, highlighting the dimensional dependence and calculating the finite thermal conductivity.

Findings

Magnons are localized in 2D with a diverging localization length at low frequencies.

Magnons are delocalized in 3D and exhibit diffusive motion at long wavelengths.

The thermal conductivity of Mattis glass is finite due to slow divergence of the diffusion constant.

Abstract

We study the spectral and transport properties of magnons in a model of a disordered magnet called Mattis glass, at vanishing average magnetization. We find that in two dimensional space, the magnons are localized with the localization length which diverges as a power of frequency at small frequencies. In three dimensional space, the long wavelength magnons are delocalized. In the delocalized regime in 3d (and also in 2d in a box whose size is smaller than the relevant localization length scale) the magnons move diffusively. The diffusion constant diverges at small frequencies. However, the divergence is slow enough so that the thermal conductivity of a Mattis glass is finite, and we evaluate it in this paper. This situation can be contrasted with that of phonons in structural glasses whose contribution to thermal conductivity is known to diverge (when inelastic scattering is neglected).