Acoustic spin-Chern topological Anderson insulators

Recent breakthroughs in topological Anderson insulators (TAIs) have revealed the counterintuitive possibility that sufficiently strong disorder can induce nontrivial topology from a trivial phase. Previous experimental research on TAIs has mainly focused on Chern-type and higher-order systems. However, the observation of spin-Chern-type TAI hosting disorder-induced spin-dependent boundary states remains unexplored. Here, we report on the experimental realization of a spin-Chern-type TAI in a two-dimensional bilayer phononic crystal. We directly observe evidence of TAI through disorder-induced pseudospin-dependent helical boundary modes from a trivial insulator and further demonstrate their robustness. By extending topological descriptions to disordered supercells and capturing the spin-Bott index, we confirm the topological Anderson phase transition. This work opens different perspectives for the realization of interesting topological phases in optics, circuits, and cold atom systems.

Automated summary

Recent progress in studying topological Anderson insulators (TAIs) has shown that strong disorder can induce nontrivial topology from a trivial phase. In this study, a spin-Chern-type TAI was experimentally realized in a two-dimensional bilayer phononic crystal, and disorder-induced pseudospin-dependent helical boundary modes were observed. The robustness of these boundary modes was demonstrated, and the topological Anderson phase transition was confirmed by extending topological descriptions to disordered supercells and capturing the spin-Bott index. This work offers new perspectives for realizing interesting topological phases in optics, circuits, and cold atom systems.