Magnon-Photon Bound States Interactions in a Coupled-Cavity Array

Coupled-cavity array (CCA), the discrete analogs of photonic crystal waveguide, offer precise control over dispersion, band gaps, and localized photonic modes, enabling engineered photon transport and light–matter interaction. Although CCA have been widely employed to mediate interactions among atoms and solid-state emitters, their integration with magnonic systems remains largely unexplored. Here, we investigate a CCA magnonic system by coupling two spatially separated yttrium iron garnet (YIG) spheres to a one-dimensional CCA. The magnon modes hybridize with CCA band-edge modes to form photonic bound states with tunable spatial localization. These bound states mediate long-range coherent and dissipative magnon–magnon interactions, even when the YIG spheres are separated by many lattice sites. By varying the YIG positions, we control the interaction strength and coherence through the bound-state localization profile; by tuning the magnon frequencies, we selectively excite different bound-state modes and achieve frequency-controlled interaction engineering. These results establish CCAs as a versatile platform for realizing long-range, tunable magnonic coupling, opening opportunities for reconfigurable magnonic networks and hybrid quantum technologies.