Corner states in a second-order mechanical topological insulator

Demonstration of topological boundary modes in elastic systems has attracted a great deal of attention over the past few years due to its unique protection characteristic. Recently, second-order topological insulators have been proposed in manipulating the topologically protected localized states emerging only at corners. Here, we numerically and experimentally study corner states in a two-dimensional phononic crystal, namely a continuous elastic plate with embedded bolts in a hexagonal pattern. We create interfacial corners by adjoining trivial and non-trivial topological configurations. Due to the rich interaction between the bolts and the continuous elastic plate, we find a variety of corner states of and devoid of topological origin. Strikingly, some of the corner states are not only highly-localized but also tunable. Taking advantage of this property, we experimentally demonstrate asymmetric corner localization in a Z-shaped domain wall. This finding could create interest in exploration of tunable corner states for the use of advanced control of wave localization. Topological boundary modes in mechanical systems have recently attracted great attention due to their unique protection features. Here, tunable corner localization of mechanical waves is numerically and experimentally demonstrated in a continuous elastic plate with hexagonally arranged bolts.

Automated summary

Corner states in a two-dimensional phononic crystal were studied, revealing highly localized and tunable properties. This finding could spark interest in exploring tunable corner states for advanced wave localization control.