Strong Magnon-Phonon Coupling in the Kagome Antiferromagnets

Magnon-phonon hybridization in ordered materials is a crucial phenomenon with significant implications for spintronics, magnonics, and quantum materials research. We present direct experimental evidence and theoretical insights into magnon-phonon coupling in Mn_{3}Ge, a kagome antiferromagnet with noncollinear spin order. Using inelastic x-ray scattering and ab initio modeling, we uncover strong hybridization between planar spin fluctuations and transverse optical phonons, resulting in a large hybridization gap of ∼2 meV. This coupling is driven by interlayer Heisenberg exchange interactions and is enhanced by the material's symmetry and magnetic frustration. The simplicity of the Mn_{3}Ge structure enables clear identification of the hybridized modes, bridging theoretical predictions and experimental observations. Our findings establish Mn_{3}Ge as a model system for exploring magnon-phonon interactions and offer a pathway for designing materials with tunable magnetoelastic properties.