Symmetry Approach to Chiral Optomagnonics in Antiferromagnetic Insulators

TL;DR

This paper explores the symmetry-based analogy between optical and magnetic phenomena in antiferromagnetic insulators, revealing new insights into chiral optomagnonics and magnonic spin photocurrents.

Contribution

It introduces a symmetry framework linking spin waves and electromagnetic fields, extending optical chirality concepts to antiferromagnetic materials and analyzing photo-excitation mechanisms.

Findings

Spin waves and electromagnetic fields share symmetry properties.

Optical chirality concepts are extended to antiferromagnetic insulators.

Circularly polarized light can excite magnonic spin currents.

Abstract

We discuss several aspects of chiral optomagnonics in antiferromagnetic insulators by considering common symmetries between the electromagnetic field and spin excitations. This approach allows us to look at optical and magnetic materials from similar perspectives, and discuss useful analogies between them. We show that spin waves in collinear antiferromagnets and the electromagnetic field in vacuum are both invariant under the same eight-dimensional algebra of symmetry transformations. By such analogy, we can extend the concept of optical chirality to antiferromagnetic insulators, and demonstrate that the spin-wave dynamics in these materials in the presence of a spin current is similar to that of the light inside chiral metamaterials. Photo-excitation of magnonic spin currents is also discussed from the symmetry point of view. It is demonstrated that a direct magnonic spin photocurrent can be exited by circularly polarized light, which can be considered as a magnonic analogue of the photogalvanic effect. We also note that the Zitterbewegung process should appear and may play a role in photo-excitation processes.