Anomalous energy transport in laminates with exceptional points

Abstract

Recent interest in metamaterials has led to a renewed study of wave mechanics in different branches of physics. Elastodynamics involves a special intricacy, owing to a coupling between the volumetric and shear parts of the elastic waves. Through a study of in-plane waves traversing periodic laminates, we here show that this coupling can result with unusual energy transport. We find that the corresponding frequency spectrum contains modes which simultaneously attenuate and propagate, and demonstrate that these modes coalesce to purely propagating modes at exceptional points, a property that was recently reported in parity-time symmetric systems. We show that the laminate exhibits metamaterial features near these points, such as negative refraction, and beam steering and splitting. While negative refraction in laminates has been demonstrated before by considering pure shear waves impinging an interface with multiple layers, here we realize it for coupled waves impinging a simple single-layer interface. This feature, together with the appearance of exceptional points, are absent from the model problem of anti-plane shear waves which have no volumetric part, and hence from the mathematically identical electromagnetic waves. Our work further paves the way for applications such as asymmetric mode switches, by encircling exceptional points in a tangible, purely elastic apparatus.

arXiv comment35 pages, 28 figures

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Cited by in corpus (13)

• Non-Hermitian Physics
• Observation of anti-parity-time-symmetry, phase transitions and exceptional points in an optical fibre
• Scattering under Linear Non Self-Adjoint Operators: Case of in-Plane Elastic Waves
• Linking scalar elastodynamics and non-Hermitian quantum mechanics
• Discrete One-dimensional Models for the Electromomentum Coupling
• Giant Amplification of Small Perturbations in Frictional Amorphous Solid
• The Atomistic Green's Function method for acoustic and elastic wave-scattering problems
• Emergence of Exceptional Points in Periodic Metastructures with Hidden PT-symmetric Defects
• Symmetry-driven Phononic Metamaterials
• Fundamental principles for generalized Willis metamaterials
• Oblique scattering from non-Hermitian optical waveguides
• Surface corrugated laminates as elastic grating couplers: splitting of SV- and P-waves by selective diffraction
• In-Plane Linear Stress Waves in Layered Media: I. Non-Hermitian Degeneracies and Modal Chirality