Experimental study demonstrates disorder-induced spin-dependent helical boundary states in bilayer phononic crystals, indicating robust acoustic spin-Chern topological Anderson phases.
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.
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Liu et al. (2023) studied this question.
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