Topological Chiral Phonons Along The Line Defect Of Intralayer Heterojunctions

As a potential degree of freedom, the chirality of phonons is expected to become a carrier of information. Exploring the phonon mode that can stably maintain chirality along a certain transport path is the basis for its realization. In this work, we find a chiral interface mode that is obviously localized at the line defect in the hexagonal boron nitride intralayer heterojunction, which is topologically protected. The existence of mirror symmetry results in the mode having opposite chiralities on both sides of the interface. For the B-B and N-N interface configurations, the chiral mode at the heavy-atom interface is more localized, which is determined by the local symmetry and atomic vibration intensity. By applying different harmonic forces, the topological chiral phonons at two valleys can be selectively excited and can be directionally transmitted without dissipation. With the decrease of the size of the heterojunction nanoribbon, the chiral interface mode always exists in the structurally stable systems. Our work enriches the research of chiral phonons in quasi-one-dimensional systems and can also provide certain references for the design of chiral phonon devices.