Unidirectional zero sonic reflection in passive $\mathcal{P}\mathcal{T}$ symmetric Willis media

Abstract

In an effective medium description of acoustic metamaterials, the Willis coupling plays the same role as the bianisotropy in electromagnetism. Willis media can be described by a constitutive matrix composed of the classical effective bulk modulus and density and additional cross-coupling terms defining the acoustic bianisotropy. Based on an unifying theoretical model, we unite the properties of acoustic Willis coupling with $\mathcal{P}\mathcal{T}$ symmetric systems under the same umbrella and show in either case that an exceptional point hosts a remarkably pronounced scattering asymmetry that is accompanied by one-way zero reflection for sound waves. The analytical treatment is backed up by experimental input in asymmetrically side-loaded wavesguides showing how gauge transformations and loss biasing can embrace both Willis materials and non-Hermitian physics to tailor unidirectional reflectionless acoustics, which is appealing for purposeful sound insulation and steering.

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Cited by in corpus (17)

• Anomalous energy transport in laminates with exceptional points
• Symmetry-Protected Scattering in Non-Hermitian Linear Systems
• Symmetry Breaking Creates Electro-Momentum Coupling in Piezoelectric Metamaterials
• Acoustic amplifying diode using non-reciprocal Willis coupling
• Acoustic Multifunctional Logic Gates and Amplifier based on Passive Parity-Time Symmetry
• Linking scalar elastodynamics and non-Hermitian quantum mechanics
• Realizing spatiotemporal effective media for acoustic metamaterials
• Non-symmetric flexural wave scattering and one-way extreme absorption
• Discrete One-dimensional Models for the Electromomentum Coupling
• Spectral and transport properties of a $\mathcal{P}\mathcal{T}$-symmetric tight-binding chain with gain and loss
• Multi-functional resonant acoustic networks for wave routing
• Symmetry-driven Phononic Metamaterials
• Fundamental principles for generalized Willis metamaterials
• Acoustic scattering singularities via quasi-Bound states in the continuum
• In-Plane Linear Stress Waves in Layered Media: I. Non-Hermitian Degeneracies and Modal Chirality
• Acoustic Willis metamaterials beyond the passivity bound
• Bidirectional acoustic negative refraction based on a pair of metasurfaces with both local and global PT-symmetries