We show how amplitude modulated, coherent high-frequency drives can be used to access otherwise difficult to reach collective resonances and off-resonantly induce parametric instabilities. In particular, we demonstrate that difficult to access antiferromagnetic resonances in the THz range can be parametrically excited with signals at optical frequencies via a mechanism that we call Modulated Floquet Parametric Driving (MFPD). We study spin pumping and the formation of entangled, two-mode squeezed magnon pairs in anisotropic antiferromagnets under MFPD. Furthermore, we show that MFPD induces transitions to symmetry breaking steady-states in which dynamical spin patterns are formed by resonant magnon pairs.
@article{arxiv.2507.08147,
title = {Exciting terahertz magnons with amplitude modulated light: spin pumping, squeezed states, symmetry breaking and pattern formation},
author = {Egor I. Kiselev and Jonas F. Karcher and Mark S. Rudner and Rembert Duine and Netanel H. Lindner},
journal= {arXiv preprint arXiv:2507.08147},
year = {2025}
}