Spectral flow of a localized mode in elastic media

TL;DR

This paper introduces a novel real-space topological approach to achieve and control localized elastic waves in continuous media, demonstrated through theoretical prediction and experimental validation of spectral mode flow.

Contribution

It presents a new general theory based on real-space topology for localized wave modes in elastic media, overcoming limitations of previous design methods.

Findings

Spectral flow of localized mode demonstrated experimentally.

Single-parameter modulation achieves mode control.

Approach applicable to various elastic structures.

Abstract

The introduction of structural defects in otherwise periodic media is well known to grant exceptional space control and localization of waves in various physical fields, including elasticity. Despite the variety of designs proposed so far, most of the approaches derive from contextual modifications that do not translate into a design paradigm due to the lack of a general theory. Few exceptions include designs endowed with topological dispersion bands, which, however, require changes over substantial portions of the structure. To overcome these limitations, here we introduce a new rationale based on real-space topology to achieve localized modes in continuous elastic media. We theoretically predict and experimentally demonstrate the spectral flow of a localized mode across a bulk frequency gap by modulating a single structural parameter at any chosen location in the structure. The simplicity and generality of this approach opens new avenues in designing wave-based devices for energy localization and control.