Active control of localized mode and transmission in topological phononic waveguides by non-Hermitian modulation

We demonstrate the switching behavioral differences between lossy and nearly lossless edge-mode propagation by non-Hermitian modulation based on the phononic band design of a C3v symmetric, two-dimensional phononic crystal with a unit cell composed of three air-filled circular holes in polydimethylsiloxane. We numerically show that strong loss effects lead to the extinction of the localized modes. This mechanism is analogous to the bound-to-unbound transition in non-Hermitian quantum systems. This result suggests that large variations in non-Hermitian modulation can be used for the active control of edge-mode propagation along topological interfaces.