Magnon spin transport around the compensation magnetic field in easy-plane antiferromagnetic insulators

TL;DR

This paper theoretically investigates magnon spin transport in easy-plane antiferromagnetic insulators, revealing how an external magnetic field can compensate anisotropy effects, enabling control over magnon dynamics and activating the magnon spin Hall effect.

Contribution

It demonstrates the full compensation of band splitting by an external field in easy-plane antiferromagnets, activating the magnon spin Hall effect and enabling field control of magnon spin transport.

Findings

Magnetic anisotropy band splitting can be fully compensated by an external magnetic field.

The magnon spin Hall effect can be activated in easy-plane antiferromagnets.

Field control over magnon spin lifetime and diffusion length is possible.

Abstract

In this work, we theoretically study the magnon spin transport in easy-plane antiferromagnetic insulators in the presence of an in-plane magnetic field. By exactly calculating the magnon spectrum, we find the band splitting due to the magnetic anisotropy can be fully compensated by the external field at a particular strength, which makes its dynamics nearly equivalent to an easy-axis antiferromagnet. As a result, the intrinsic magnon spin Hall effect due to the dipole-dipole interaction, previously predicted in easy-axis antiferromagnets is activated in easy-plane antiferromagnets. The compensation feature also allows the field control of magnon spin lifetime and hence the spin diffusion length. The compensation feature is robust against the biaxial anisotropy.