Novel magnetic excitations beyond the single- and double-magnons
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 α-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.