One-way topological edge states in nonlinear gyroscopic phononic crystals

Abstract: A unified form of time-reversal symmetry (TRS) breaking terms in phononic crystals, leading to nontrivial phononic topology, has been proposed recently, but is contradicted by some other works which introduce gyroscopic effect as TRS-breaking. We re-study gyroscopic phononic crystals using Newtonian mechanical method, and find the correct TRS-breaking term in consistent with the unified form. Applying this term we calculate the basic topological phononics in a honeycomb lattice. Furthermore, we study nonlinear phonon-phonon scattering effect on topological phononic edge states by molecular dynamics simulation. Generally edge states are not immune to such scattering effect, but under specific conditions some edge states run into bulk much more slowly, depending on the parameters of the model. This opens up the potential for effectively suppressing phonon dissipation by tuning the parameters, thereby realizing near-100% efficiency of one-way phonon transport in phonon devices.