# Pumping of magnons in a Dzyaloshinskii-Moriya ferromagnet

## TL;DR

This paper develops a microscopic linear response theory for magnonic torques and pumping in Dzyaloshinskii-Moriya ferromagnets, revealing intrinsic Berry curvature effects and reciprocity relations, with applications to honeycomb and kagome lattices.

## Contribution

It introduces a novel linear response framework that accounts for Berry curvature and Dzyaloshinskii-Moriya interactions in magnonic systems, linking torques and heat pumping.

## Key findings

- Dzyaloshinskii-Moriya interactions act as fictitious electric fields on magnons.
- Intrinsic contributions are expressed via Berry curvature of magnonic bands.
- Established Onsager reciprocity between magnon-mediated torques and heat pumping.

## Abstract

We formulate a microscopic linear response theory of nonequilibrium magnonic torques and magnon pumping applicable to multiple-magnonic-band uniform ferromagnets with Dzyaloshinskii-Moriya interactions. From the linear response theory, we identify the extrinsic and intrinsic contributions where the latter is expressed via the Berry curvature of magnonic bands. We observe that in the presence of a time-dependent magnetization Dzyaloshinskii-Moriya interactions can act as fictitious electric fields acting on magnons. We study various current responses to this fictitious field and analyze the role of Berry curvature. After identifying the magnon-mediated contribution to the equilibrium Dzyaloshinskii-Moriya interaction, we also establish the Onsager reciprocity between the magnon-mediated torques and heat pumping. We apply our theory to the magnonic heat pumping and torque responses in honeycomb and kagome lattice ferromagnets.