Line Waves Existing at Junctions of Dual-Impedance Metasurfaces

Line waves (LWs) are special electromagnetic modes supported on junctions of different metasurfaces that enforce a duality condition, such as capacitive and inductive metasurfaces. These edge modes are tightly confined to the interface and can propagate along arbitrary one-dimensional paths with high efficiency. Such attractive characteristics show potential applications for robust waveguides. Here, we introduce a compact dual-impedance metasurface platform to explore the properties of LWs. We explore intrinsic properties of LWs including dispersion, confinement, and spin-momentum locking. It is found that broadband LWs can be supported by metasurfaces with varied surface wave momentum, and the dispersion of LWs can be tailored by tuning either their capacitive or inductive properties. The equivalent impedances of metasurfaces are extracted to establish a simplified semianalytical model to study their spin-momentum locking properties. Unidirectional propagation can be excited via a chiral point source placed near the junction. We further implement a parallel plate waveguide consisting of four metasurfaces arranged with a duality symmetry. Experiments validate the analysis and indicate the existence of highly robust transmissions even when the waveguide is longitudinally warped, providing an enticing option for applying LWs in the field of wearable wireless channels and flexible electronics.