Non-Hermitian elastic waveguides with piezoelectric feedback actuation: non-reciprocal bands and skin modes

Abstract

In this work, we investigate non-Hermitian elastic waveguides with periodically applied proportional feedback efforts, implemented through piezoelectric sensors and actuators. Using onedimensional spectral models for longitudinal motion, it is shown that dispersion diagrams of this family of structures exhibit non-reciprocal imaginary frequency components, manifesting as wave attenuation or amplification along opposite directions for all pass bands. The effects of positive and negative proportional feedback, as well as local and non-local actuation are investigated. Overall, switching the sign of the feedback effort inverts the amplification direction, while increasing the degree of non-locality produces splitting of the pass bands into multiple bands with interchanging non-reciprocal behavior. Furthermore, skin modes localized at the boundaries of finite domains are investigated and successfully predicted by the winding number of the complex dispersion bands. These results contribute to recent efforts in designing metamaterials with novel properties associated with the physics of non-Hermitian systems, which may find fruitful technological applications relying on vibration and noise control, wave localization, filtering and multiplexing.

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Cited by in corpus (9)

• Topological Non-Hermitian skin effect
• Observation of exceptional points and skin effect correspondence in non-Hermitian phononic crystals
• Sensitivity of non-Hermitian systems
• Non-Bloch band theory of generalized eigenvalue problems
• Complex Spatiotemporal Modulations and Non-Hermitian Degeneracies in $\mathcal{P}\mathcal{T}$-Symmetric Phononic Materials
• Non-dispersive one-way signal amplification in sonic metamaterials
• Harnessing $\mathcal{P}\mathcal{T}$-symmetry in non-Hermitian stiffness-modulated waveguides
• Brillouin-zone definition in non-reciprocal Willis monatomic lattices
• Non-Local Elastic Lattices with $\mathcal{P}\mathcal{T}$-Symmetry and Time Modulation: From Perfect Trapping to the Wave Boomerang Effect