Topologically protected acoustic helical edge states and interface states in strongly coupled metamaterial ring lattices

TL;DR

This paper demonstrates the first acoustic topological insulator using a metamaterial ring lattice that supports one-way, backscattering-immune edge states and spin-filtered interface states, advancing robust wave transport in acoustics.

Contribution

It introduces a novel acoustic topological insulator based on a strongly coupled metamaterial ring lattice supporting helical edge states under time-reversal symmetry.

Findings

Supports one-way acoustic edge states immune to boundary variations

Demonstrates spin-filtered interface states due to lattice dislocations

Mechanism applicable to other wave systems and higher dimensions

Abstract

Time reversal (T) invariant topological insulator is widely recognized as one of the fundamental discoveries in condensed matter physics, for which the most fascinating hallmark is perhaps a spin based topological protection, the total cancellation of scattering of conduction electrons with certain spins on matter surface. Recently, it has created a paradigm shift for topological insulators, from electronics to photonics, phononics as well as mechanics, bringing about not only involved new physics but also potential applications in robust wave transport. Despite the growing interests in realizing topologically protected acoustic wave transport, T-invariant acoustic topological insulator has not yet been achieved. Here, we report the first demonstration of acoustic topological insulator: a strongly coupled metamaterial ring lattice that supports one-way propagation of helical edge states under T-symmetry, backscattering immune to boundary abrupt variations. The very unique thing is the formation of spin-filtered interface states due to lattice dislocations. The mechanism underlying the formation of topologically protected edge states and interface states is applicable in various other wave systems or higher dimensions.