Strong coupling between distinct quasiparticles in condensed matter systems gives rise to hybrid states with emergent properties. We demonstrate the hybridization of confined phonons and finite-wavelength magnons, forming a magnon-polaron cavity with tunable coupling strength and spatial confinement controlled by the applied magnetic field direction. Our platform consists of a low-loss, single-crystalline yttrium iron garnet (YIG) film coupled to a zinc oxide (ZnO)-based surface acoustic wave (SAW) resonator. This heterostructure enables exceptionally low magnon-polaron dissipation rates below κ/2π<1.5MHz. The observed mode hybridization is well described by a phenomenological model incorporating the spatial profiles of magnon and phonon modes. Furthermore, we report the first observation of Rabi-like oscillations in a coupled SAW-spin wave system, revealing the dynamical formation of magnon-polarons in the time domain. These results establish a platform for engineering hybrid spin-acoustic excitations in extended magnetic systems and enable time-resolved studies of magnon-polaron states.
@article{arxiv.2506.09717,
title = {Magnon-polaron control in a surface magnetoacoustic wave resonator},
author = {Kevin Künstle and Yannik Kunz and Tarek Moussa and Katharina Lasinger and Kei Yamamoto and Philipp Pirro and John F. Gregg and Akashdeep Kamra and Mathias Weiler},
journal= {arXiv preprint arXiv:2506.09717},
year = {2026}
}