Exceptional coupling via multiple channels for crosstalk suppression and flat band with staggered on-site potentials

Precise control of near-field coupling is essential for advancing technologies such as antenna arrays, waveguide systems, and optical networks, as well as for studying physical phenomena like mode hybridization and energy transfer. However, achieving exceptional coupling (EC)—defined as effective zero coupling—remains difficult because strong near-field interactions arise at short distances, limiting the ability to suppress crosstalk in integrated systems. Here we show that EC can be realized in a multi-resonator system by introducing a detuned relay resonator that cancels both direct and indirect coupling pathways. This hybrid near-field strategy also enables the formation of a flat band with staggered on-site potentials in periodic structures, offering a route to electromagnetic shielding without relying on conventional blocking materials. Our theoretical analysis and experiments confirm the effectiveness of this method, which is scalable and applicable to integrated antenna and optical waveguide arrays, providing unique opportunities for compact and efficient electromagnetic devices. Controlling how nearby resonators exchange energy is crucial for reducing interference in compact communication and sensing devices. The authors demonstrate a method that cancels different coupling paths, achieving “exceptional coupling” and flat bands, which suppress crosstalk and enable robust signal control in integrated systems.