Some non-Hermitian and modulated acoustic topological crystals

Topological acoustics was introduced over a decade ago, with recent research increasingly focusing on non-Hermitian and modulated acoustic crystals. In this talk, we introduce some of our recent advancements in this direction. First, we explore a one-dimensional (1-D) acoustic crystal with disorder applied to the nearest-neighbor couplings. Such a disorder can induce non-Hermitian point-gap topology and localize all waves at a boundary, which challenges the conventional picture of Anderson localization. Second, we discuss the gap closure in such a non-Hermitian crystal and demonstrate the non-Hermitian edge burst. Finally, we illustrate the concept of delicate topology and demonstrate it with returning Thouless pumping in a 1-D acoustic crystal.