Novel magnetic excitations beyond the single- and double-magnons

TL;DR

This paper uncovers higher-rank magnons carrying multiple units of spin angular momentum in { extalpha}-Fe2O3, demonstrating photon-driven creation of exotic quasiparticles beyond conventional single- and double-magnons.

Contribution

It reveals the existence of higher-rank magnons generated by two-photon processes, expanding understanding of angular momentum transfer in magnetic systems.

Findings

Discovered cascade of higher-rank magnons with multiple spin units

Demonstrated two-photon scattering can create exotic quasiparticles

Revealed potential applications in magnon-based technologies

Abstract

Conventional wisdom suggests that one photon that carries one unit of angular momentum can change the spin angular momentum of a magnetic system with one unit (delta Ms = +-1) at most. This would imply that a two-photon scattering process can manipulate the spin angular momentum of the magnetic system with a maximum of two units. Here we examine the fundamental limit of the photon-driven transport of angular momentum by studying the magnon spectrum of {\alpha}-Fe2O3 using resonant inelastic x-ray scattering. We discovered a cascade of higher-rank magnons carrying double, triple, quadruple, and quintuple the spin angular momentum of a single-magnon. Guided by theoretical calculations, we reveal how a two-photons scattering process can create exotic higher-rank magnons and the relevance of these quasiparticles for magnon-based applications.