Sum-frequency excitation of coherent magnons

TL;DR

This paper introduces sum-frequency excitation mechanisms for coherent magnon control, expanding the understanding of spin dynamics beyond traditional difference-frequency Raman processes, with potential for more efficient excitation methods.

Contribution

It demonstrates how sum-frequency components can coherently excite magnons, providing a new approach to spin control using linearly polarized fields.

Findings

Sum-frequency mechanisms can achieve excitation efficiencies comparable or superior to Raman techniques.

Linearly polarized fields enable effective sum-frequency magnon excitation.

Elliptical and circular polarizations produce weak or no sum-frequency excitation.

Abstract

Coherent excitation of magnons is conventionally achieved through Raman scattering processes, in which the difference-frequency components of the driving field are resonant with the magnon energy. Here, we describe mechanisms by which the sum-frequency components of the driving field can be used to coherently excite magnons through two-particle absorption processes. We use the Landau-Lifshitz-Gilbert formalism to compare the spin-precession amplitudes that different types of impulsive stimulated and ionic Raman scattering processes and their sum-frequency counterparts induce in an antiferromagnetic model system. We show that sum-frequency mechanisms enabled by linearly polarized driving fields yield excitation efficiencies comparable or larger than established Raman techniques, while elliptical polarizations produce only weak and circularly polarizations no sum-frequency components at all. The mechanisms presented here complete the map for dynamical spin control by the means of Raman-type processes.