Topological defect states in elastic phononic plates

TL;DR

This paper explores how topological defects like disclinations and dislocations in elastic phononic plates create robust, localized wave states that are immune to disturbances, opening new avenues in topological mechanics.

Contribution

It introduces topological defect states in elastic phononic plates, demonstrating their ability to produce protected waveguides and resonators with robustness against disturbances.

Findings

Topological defect states localize around defect boundaries.

Interface states are immune to finite size effects.

Disclinations produce pentagonal core structures with localized states.

Abstract

Topological defects (including disclinations and dislocations) which commonly exist in various materials have shown an amazing ability to produce excellent mechanical and physical properties of matters. In this paper, disclinations and dislocations are firstly introduced into the valley-polarized elastic phononic plate. Deformation of the lattice yields the interface expressing as the topologically protected wave guiding, due to the valley-polarized phase transition of phononic crystals (PnCs) across the interface. Then, disclinations are introduced into the Wannier-type elastic phononic plate. The deformation of the lattice yielded by disclinations produces a pentagonal core with the local five-fold symmetry. The topological bound states are well localized around the boundaries of the pentagonal cores with and without the hollow regions. The topological interface state and the topological bound state immunize against the finite sizes and the moderate disturbances of plates, essentially differing from the trivial defect states. The discovery of topological defect states unveils a new horizon in topological mechanics and physics, and it provides a novel platform to implement large-scale elastic devices with robust topological waveguides and resonators.