Nonabelian magnonics in antiferromagnets

TL;DR

This paper develops a semiclassical formalism for antiferromagnetic magnonics emphasizing spin wave chirality, revealing nonabelian dynamics that could enable new logic operations in AFM spin wave systems.

Contribution

It introduces a chirality-centric formalism with magnonic isospin as a fundamental concept, unifying AFM magnonics and demonstrating nonabelian spin wave operations.

Findings

Isospin governed by unitary Hamiltonian evolution

Spin wave operations form a nonabelian group

Potential for new AFM spin wave logic families

Abstract

We present a semiclassical formalism for antiferromagnetic (AFM) magnonics which promotes the central ingredient of spin wave chirality, encoded in a quantity called magnonic isospin, to a first-class citizen of the theory. We use this formalism to unify results of interest from the field under a single chirality-centric formulation. Our main result is that the isospin is governed by unitary time evolution, through a Hamiltonian projected down from the full spin wave dynamics. Because isospin is SU(2)-valued, its dynamics on the Bloch sphere are precisely rotations - which, in general, do not commute. Consequently, the induced group of operations on AFM spin waves is nonabelian. This is a paradigmatic departure from ferromagnetic magnonics, which operates purely within the abelian group generated by spin wave phase and amplitude. Our investigation of this nonabelian magnonics in AFM insulators focuses on studying several simple gate operations, and offering in broad strokes a program of study for interesting new logic families in antiferromagnetic spin wave systems