Inplane anisotropy of longitudinal thermal conductivities and weak localization of magnons in a disordered spiral magnet

TL;DR

This paper investigates how disorder and Dzyaloshinsky-Moriya interactions cause anisotropic thermal conductivity and weak localization of magnons in a disordered spiral magnet, providing insights into magnetic transport phenomena.

Contribution

It introduces a theoretical framework for analyzing anisotropic thermal conductivities and magnon weak localization in disordered spiral magnets using linear response and spin-wave approximations.

Findings

Thermal conductivity is anisotropic due to Dzyaloshinsky-Moriya interaction.

Weak localization causes logarithmic suppression of magnon transport.

Results suggest ubiquity of magnon localization in disordered 2D magnets with time-reversal symmetry.

Abstract

We demonstrate the inplane anisotropy of longitudinal thermal conductivities and the weak localization of magnons in a disordered screw-type spiral magnet on a square lattice. We consider a disordered spin system, described by a spin Hamiltonian for the antiferromagnetic Heisenberg interaction and the Dzyaloshinsky-Moriya interaction with the mean-field type potential of impurities. We derive longitudinal thermal conductivities for the disordered screw-type spiral magnet in the weak-localization regime by using the linear-response theory with the linear-spin-wave approximation and performing perturbation calculations. We show that the inplane longitudinal thermal conductivities are anisotropic due to the Dzyaloshinsky-Moriya interaction. This anisotropy may be useful for experimentally estimating the magnitude of a ratio of the Dzyaloshinsky-Moriya interaction to the Heisenberg interaction. We also show that the main correction term gives a logarithmic suppression with the length scale due to the critical back scattering. This suggests that the weak localization of magnons is ubiquitous for the disordered two-dimensional magnets having global time-reversal symmetry. We finally discuss several implications for further research.