Elastic Gauge Fields and Hall Viscosity of Dirac Magnons

TL;DR

This paper explores how elastic deformations influence magnon Dirac materials, revealing elastic gauge fields, pseudoLandau levels, and a magnon Hall viscosity response linked to topological effects and temperature.

Contribution

It demonstrates the emergence of elastic gauge fields and Hall viscosity in magnon Dirac materials, incorporating topological effects and temperature dependence, extending concepts from graphene to magnetic systems.

Findings

Elastic gauge fields couple to magnon pseudospinors.

Constant pseudomagnetic fields induce pseudoLandau levels.

Magnon Hall viscosity depends on temperature and magnon population.

Abstract

We analyze the coupling of elastic lattice deformations to the magnon degrees of freedom of magnon Dirac materials. For a Honeycomb ferromagnet we find that, as it happens in the case of graphene, elastic gauge fields appear coupled to the magnon pseudospinors. For deformations that induce constant pseudomagnetic fields, the spectrum around the Dirac nodes splits into pseudoLandau levels. We show that when a Dzyaloshinskii-Moriya interaction is considered, a topological gap opens in the system and a Chern-Simons effective action for the elastic degrees of freedom is generated. Such a term encodes a phonon Hall viscosity response, entirely generated by fluctuations of magnons living in the vicinity of the Dirac points. The magnon Hall viscosity vanishes at zero temperature, and grows as temperature is raised and the states around the Dirac points are increasingly populated.