Magnetic excitations beyond the single- and double-magnons.

Authors :: Elnaggar H
Nag A
Haverkort MW
Garcia-Fernandez M
Walters A
Wang RP
Zhou KJ
de Groot F
Source :: Nature communications [Nat Commun] 2023 May 12; Vol. 14 (1), pp. 2749. Date of Electronic Publication: 2023 May 12.
Publication Year :: 2023
Abstract: A photon carrying one unit of angular momentum can change the spin angular momentum of a magnetic system with one unit (ΔM <subscript>s</subscript> = ±1) at most. This implies that a two-photon scattering process can manipulate the spin angular momentum of the magnetic system with a maximum of two units. Herein we describe a triple-magnon excitation in α-Fe <subscript>2</subscript> O <subscript>3</subscript> , which contradicts this conventional wisdom that only 1- and 2-magnon excitations are possible in a resonant inelastic X-ray scattering experiment. We observe an excitation at exactly three times the magnon energy, along with additional excitations at four and five times the magnon energy, suggesting quadruple and quintuple-magnons as well. Guided by theoretical calculations, we reveal how a two-photon scattering process can create exotic higher-rank magnons and the relevance of these quasiparticles for magnon-based applications.<br /> (© 2023. The Author(s).)