Observation of Long-Lifetime Magnon Pairs by Fano Resonance of Photons

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Main Authors: Huang, Qian-Nan, Xue, Zhiping, Yu, Tao
Format: Preprint
Published: 2025
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author Huang, Qian-Nan
Xue, Zhiping
Yu, Tao
author_facet Huang, Qian-Nan
Xue, Zhiping
Yu, Tao
contents Mode fluctuations with a long lifetime are essential for quantum information and logic operations in magnonic devices. We probe the broadband nonlinear magnetization dynamics of a high-quality ferromagnet under a strong microwave drive using microwave spectroscopy. We observe an \textit{unexpected} Fano resonance in the microwave transmission when the driven amplitude of the magnetization is large and the drive frequency $ω_d$ is close to but not at the ferromagnetic resonance. We interpret this Fano resonance by a scattering theory of photons considering the three-magnon interaction between the Kittel magnon and magnon pairs with opposite wave vectors of frequency $ω_d/2$. The theoretical model suggests that the microwave spectroscopy measures the dynamics of the fluctuation $δ\hatα$ of the Kittel magnon and $δ\hatβ_{\pm k}$ of the magnon pairs over the driven steady states, which are coupled coherently by the steady-state amplitudes. With the damping of $δ\hatβ_{\pm k}$ much smaller than that of $δ\hatα$, the theoretical calculation well reproduces the observed Fano resonance, indicating the magnon pairs hold a recorded long lifetime.
format Preprint
id arxiv_https___arxiv_org_abs_2511_01667
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Observation of Long-Lifetime Magnon Pairs by Fano Resonance of Photons
Huang, Qian-Nan
Xue, Zhiping
Yu, Tao
Mesoscale and Nanoscale Physics
Materials Science
Mode fluctuations with a long lifetime are essential for quantum information and logic operations in magnonic devices. We probe the broadband nonlinear magnetization dynamics of a high-quality ferromagnet under a strong microwave drive using microwave spectroscopy. We observe an \textit{unexpected} Fano resonance in the microwave transmission when the driven amplitude of the magnetization is large and the drive frequency $ω_d$ is close to but not at the ferromagnetic resonance. We interpret this Fano resonance by a scattering theory of photons considering the three-magnon interaction between the Kittel magnon and magnon pairs with opposite wave vectors of frequency $ω_d/2$. The theoretical model suggests that the microwave spectroscopy measures the dynamics of the fluctuation $δ\hatα$ of the Kittel magnon and $δ\hatβ_{\pm k}$ of the magnon pairs over the driven steady states, which are coupled coherently by the steady-state amplitudes. With the damping of $δ\hatβ_{\pm k}$ much smaller than that of $δ\hatα$, the theoretical calculation well reproduces the observed Fano resonance, indicating the magnon pairs hold a recorded long lifetime.
title Observation of Long-Lifetime Magnon Pairs by Fano Resonance of Photons
topic Mesoscale and Nanoscale Physics
Materials Science
url https://arxiv.org/abs/2511.01667