Topological chiral phonons in center-stacked bilayer triangle lattices.

Since chiral phonons were found in an asymmetric two-dimensional hexagonal lattice, there has been growing interest in the study of phonon chirality, which were experimentally verified very recently in monolayer tungsten diselenide (2018 Science 359 579). In this work, we find chiral phonons with nontrivial topology in center-stacked bilayer triangle lattices. At the Brillouin-zone corners, [Formula: see text]([Formula: see text]), circularly polarized phonons and nonzero phonon Berry curvature are observed.