Valley Anisotropy in Elastic Metamaterials

TL;DR

This paper introduces elastic valley metamaterials with asymmetrical design, demonstrating tunable valley properties and topologically protected elastic wave propagation, advancing valleytronics in elastic systems.

Contribution

It presents the first realization of asymmetrical elastic valley metamaterials with tunable Berry curvature and topological insulator behavior, expanding valleytronics to elastic metamaterials.

Findings

Asymmetrical elastic valley metamaterials exhibit tunable Berry curvature.

Demonstration of topologically protected elastic wave propagation.

Creation of elastic valley topological insulators.

Abstract

Valley, as a new degree of freedom, raises the valleytronics in fundamental and applied science. The elastic analogs of valley states have been proposed by mimicking the symmetrical structure of either two-dimensional materials or photonic valley crystals. However, the asymmetrical valley construction remains unfulfilled. Here, we present the valley anisotropy by introducing asymmetrical design into elastic metamaterials. The elastic valley metamaterials are composed of bio-inspired hard spirals and soft materials. The anisotropic topological nature of valley is verified by asymmetrical distribution of the Berry curvature. We show the high tunability of the Berry curvature both in magnitude and sign enabled by our anisotropic valley metamaterials. Finally, we demonstrate the creation of valley topological insulators and show topologically protected propagation of transverse elastic waves relying on operating frequency. The proposed topological properties of elastic valley metamaterials pave the way to better understanding the valley topology and to creating a new type of topological insulators enabled by an additional valley degree of freedom.