Valley based splitting of topologically protected helical waves in elastic plates

Abstract

Topological protection offers unprecedented opportunities for wave manipulation and energy transport in various fields of physics, including elasticity, acoustics, quantum mechanics and electromagnetism. Distinct classes of topological waves have been investigated by establishing analogues with the quantum, spin and valley Hall effects. We here propose and experimentally demonstrate the possibility of supporting multiple classes of topological modes within a single platform. Starting from a patterned elastic plate featuring a double Dirac cone, we create distinct topological interfaces by lifting such degeneracy through selective breaking of symmetries across the thickness and in the plane of the plate. We observe the propagation of a new class of heterogeneous helical-valley edge waves capable of isolating modes on the basis of their distinct polarization. Our results show the onset of wave splitting resulting from the interaction of multiple topological equal-frequency wave modes, which may have significance in applications involving elastic beam-splitters, switches, and filters.

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• Band gap enhancement in periodic frames using hierarchical structures
• Valley Anisotropy in Elastic Metamaterials
• Abnormal topological refraction into free medium at sub-wavelength scale in valley phononic crystal plates
• Observations of symmetry induced topological mode steering in a reconfigurable elastic plate
• Linking scalar elastodynamics and non-Hermitian quantum mechanics
• Broadband Frequency and Spatial On-Demand Tailoring of Topological Wave Propagation Harnessing Piezoelectric Metamaterials
• Non-conventional topological band properties and gapless helical edge states in elastic phononic waveguides with Kekulé distortion
• Omnimodal topological polarization of bilayer networks: analysis in the Maxwell limit and experiments on a 3D-printed prototype
• Fully-Polarized Topological Isostatic Metamaterials in Three Dimensions
• Elastic three-dimensional metaframe for selective wave filtering and polarization control
• Valley and Valley-like Split-ring Topological Photonic Crystal
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