Observation of an acoustic non-Hermitian topological Anderson insulator

The interaction of band topology and disorder can give rise to intriguing phenomena. One paradigmatic example is the topological Anderson insulator, whose nontrivial topology is induced in a trivial system by disorders. In this study, we investigate the effect of purely non-Hermitian disorders on topological systems using a one-dimensional acoustic lattice with coupled resonators. Specifically, we construct a theoretical framework to describe the non-Hermitian topological Anderson insulator phase solely driven by disordered loss modulation. Then, the complete evolution of non-Hermitian disorder-induced topological phase transitions, from an initial trivial phase to a topological Anderson phase and finally to a trivial Anderson phase, is revealed experimentally using both bulk and edge spectra. Interestingly, topological modes induced by non-Hermitian disorders to be immune to both weak Hermitian and non-Hermitian disorders. These findings pave the way for future research on disordered non-Hermitian systems for novel wave manipulation.