Dual‐Band Acoustic Multimode Interference Mediated by Sliding Interface in Two‐Dimensional Hexagonal Phononic Crystals

Topological phononic crystals (PnCs) have fundamentally changed the manipulation of acoustic and elastic waves by utilizing various topological phases originally proposed in condensed matter, resulting in robust signal transmission that is immune to backscattering. However, research on the multimode interference (MMI) effect under multiple‐frequency operation is not fully understood. In this article, we investigate the dual‐band acoustic edge states by simply combining two PnCs with a half lattice sliding differences. It is confirmed that the dual‐band acoustic edge states could be created in the two trivial band gaps without the bulk topological phase transitions. Furthermore, by constructing the sandwiched heterostructure and making the layer number of middle PnCs limited, the coupled edge states in two band gaps are achieved and the dual‐band MMI of acoustic transport is investigated. Subsequently, based on the MMI of acoustic transport, the dual‐band acoustic splitter is designed. The results provide a simple way for the design of acoustic devices such as filters and couplers, and may contribute to advances in acoustic signal processing.