Terahertz stimulated parametric downconversion of a magnon mode in an antiferromagnet

TL;DR

This paper demonstrates terahertz-induced stimulated parametric downconversion of magnon modes in an antiferromagnet, revealing nonlinear magnon interactions crucial for future ultrahigh-bandwidth magnonic devices.

Contribution

It provides the first experimental observation of terahertz stimulated magnon downconversion and elucidates the nonlinear excitation pathways in antiferromagnetic materials.

Findings

Lower-frequency magnon mode is amplified during the process.

Polarization-selective two-dimensional terahertz spectroscopy reveals excitation pathways.

Fundamental insights into nonlinear magnonics in antiferromagnets.

Abstract

In condensed matter systems, interactions between collective modes offer avenues for nonlinear coherent manipulation of coupled excitations and quantum phases. Antiferromagnets, with their inherently coupled magnon modes, provide a promising platform for nonlinear control of microscopic spin waves and macroscopic magnetization. However, nonlinear magnon-magnon interactions have been only partially elaborated, leaving key gaps in the prospects for potential ultrahigh-bandwidth magnonic signal processing. Here, we use a pair of intense terahertz pulses to sequentially excite two distinct coherent magnon modes in an antiferromagnet and find that the magnon mode with a lower frequency undergoes amplification when the higher-frequency mode is driven. We unveil the nonlinear excitation pathways of this stimulated parametric downconversion process by using polarization-selective two-dimensional terahertz spectroscopy. Our work provides fundamental insights into nonlinear magnonics in antiferromagnets, laying the groundwork for forthcoming spintronic and magnonic devices based on nonlinear magnon-magnon interactions.