New article in Phys. Review B

Our article "Classical and quantum theory of magnonic and magnetoelastic nonlinear dynamics in continuum geometries" has just been published in Phys. Rev. B!

In this theoretical work, we derive a full theory of nonlinear dynamics in magnetoelastic systems. Our model derives equations of motion for spin wave mode amplitudes that include three-magnon and four-magnon nonlinearity, as well as linear and nonlinear interaction with acoustic modes. We analytically calculate all the rates for a thin film geometry, which is very relevant for current experiments in magnetoelasticity. We characterize high-harmonic generation as well as parametric instabilities due to all possible nonlinear mechanisms. We predict a rich magnetization spectrum where the nature of the first parametric instability strongly depends on multiple system parameters. We show how, by properly tuning the parameters, magnetoelastic nonlinearity can become the predominant mechanism for parametric instability, specifically the process of an acoustic phonon splitting into two magnons (down-conversion). We also quantize our theory and explore mean-field magnetization dynamics across the parametric instability threshold. This work is a joint effort with our colleagues in the team of J. Puebla at Kyoto University, which have observed this phonon-to-magnon downconversion process experimentally in our jointly submitted article. Our work opens a new route toward preparation of propagating quantum magnonic states.

Picture credit: M. Brühlmann