Zak-phase-inspired acoustic topological edge states on the honeycomb lattice

Abstract

The Berry phase generally plays a key role in characterizing the topological phase for quantum and classic systems. However, topological edge states in a two-dimensional acoustic system are generally characterized by nonzero Berry curvature. Here we achieve the topological phase transition characterized by zero Berry curvature, based on the phononic crystal composed of 8-metaatomic composite metamolecules. We demonstrate that the phase transition can be induced through either modulating the intervals between the adjacent metaatoms or changing their sizes. The nontrivial Zak phase ensures the existence of the acoustic topological edge states, confining sound waves along the boundaries of finite sonic crystal rather than transmitting along the interface between the two structures possessing opposite topological phases. Furthermore, the multiple topological phase transitions are simply realized thanks to the two limbic metaatoms introduced. Although the eigenfrequencies of topological edge states, which appear in the partial band gap, overlap with the bulk states, we still numerically observe the topological edge states selectively through modulating the wavenumber in real space. The proposed acoustic topological insulator may have potential applications in acoustic waveguiding and isolating.