Practical realization of chiral nonlinearity for strong topological protection

TL;DR

This paper demonstrates how nonlinear topological protection can be achieved through chiral symmetry, enabling persistent edge states in acoustic systems regardless of nonlinearity specifics, with theoretical, numerical, and experimental validation.

Contribution

It introduces a general nonlinear rule based on chiral symmetry for topological protection and experimentally realizes nonlinear topological edge states in an acoustic prototype.

Findings

Nonlinear topological edge states persist without frequency shift.

Chiral symmetry conditions extend to nonlinear environments.

Experimental validation confirms theoretical predictions.

Abstract

Nonlinear topology has been much less inquired compared to its linear counterpart. Existing advances have focused on nonlinearities of limited magnitudes and fairly homogeneous types. As such, the realizations have rarely been concerned with the requirements for nonlinearity. Here we explore nonlinear topological protection by determining nonlinear rules and demonstrate their relevance in real-world experiments. We take advantage of chiral symmetry and identify the condition for its continuation in general nonlinear environments. Applying it to one-dimensional topological lattices, we show possible evolution paths for zero-energy edge states that preserve topologically nontrivial phases regardless of the specifics of the chiral nonlinearities. Based on an acoustic prototype design with non-local nonlinearities, we theoretically, numerically, and experimentally implement the nonlinear topological edge states that persist in all nonlinear degrees and directions without any frequency shift. Our findings unveil a broad family of nonlinearities compatible with topological non-triviality, establishing a solid ground for future drilling in the emergent field of nonlinear topology.