Topological mechanics of gyroscopic metamaterials

TL;DR

This paper explores topological properties of gyroscopic metamaterials, demonstrating one-way edge modes that are robust against disorder, with potential applications in lossless acoustic waveguides.

Contribution

It introduces an active gyroscopic lattice that breaks time-reversal symmetry and shows controllable topological edge modes through lattice distortions.

Findings

Edge modes are topologically protected and propagate unidirectionally.

The direction of edge modes can be switched via lattice distortions.

Experimental demonstration of one-way acoustic waveguides.

Abstract

Topological mechanical metamaterials are artificial structures whose unusual properties are protected very much like their electronic and optical counterparts. Here, we present an experimental and theoretical study of an active metamaterial -- comprised of coupled gyroscopes on a lattice -- that breaks time-reversal symmetry. The vibrational spectrum of these novel structures displays a sonic gap populated by topologically protected edge modes which propagate in only one direction and are unaffected by disorder. We present a mathematical model that explains how the edge mode chirality can be switched via controlled distortions of the underlying lattice. This effect allows the direction of the edge current to be determined on demand. We envision applications of these edges modes to the design of loss-free, one-way, acoustic waveguides and demonstrate this functionality in experiment.