Large-Area Pseudospin and Valley Waveguide States in a Three-Layer Heterostructure System

Topological pseudospin- and valley-dependent edge states have been widely explored due to their inherent topological properties and easy implementations. Conventional methods create topological modes tightly confined at the interfaces, which hinders high-capacity energy transport and efficient interconnection with diverse devices. Here, we propose a tri-band three-layer heterostructure system supporting both large-area pseudospin- and valley-locked waveguide states. Both unidirectional excitation and backscattering-immune propagation have been demonstrated. Besides, the large-area waveguide states manifest tunable mode width, which can be potentially used for impedance matching with wave-guiding channels with different aperture widths. This work enlarges the photonic systems that could be utilized for multi-band multi-functionallarge-area-mode enabled topological devices.