Step-wise constant-amplitude waves in non-Hermitian disordered media

Zhang, Haixiao; Zhang, Yiwei; Liu, Xiaoli; Bao, Yu; Zhao, Jinyu

doi:10.1063/5.0096220

Cited by 5 publications

(3 citation statements)

References 30 publications

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“…Moreover, unidirectional transparency stemming from non-Hermitian acoustic systems can also be utilized to realize an acoustic directional cloak [104,110]. In a similar way, such unidirectional transparency can be utilized to suppress the scattering from impurity, realized by a design combing zero-index and PT -symmetry [111,169,170].…”

Section: Non-hermitian Acoustics In Waveguides (1d)mentioning

confidence: 99%

Non-local and non-Hermitian acoustic metasurfaces

Wang,

Dong,

et al. 2023

Rep. Prog. Phys.

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Acoustic metasurfaces are at the frontier of acoustic functional material research owing to their advanced capabilities of wave manipulation at an acoustically vanishing size. Despite significant progress in the last decade, conventional acoustic metasurfaces are still fundamentally limited by their underlying physics and design principles. First, conventional metasurfaces assume that unit cells are decoupled and therefore treat them individually during the design process. Owing to diffraction, however, the non-locality of the wave field could strongly affect the efficiency and even alter the behavior of acoustic metasurfaces. Additionally, conventional acoustic metasurfaces operate by modulating the phase and are typically treated as lossless systems. Due to the narrow regions in acoustic metasurfaces' subwavelength unit cells, however, losses are naturally present and could compromise the performance of acoustic metasurfaces. While the conventional wisdom is to minimize these effects, a counter-intuitive way of thinking has emerged, which is to harness the non-locality as well as loss for enhanced acoustic metasurface functionality. This has led to a new generation of acoustic metasurface design paradigm that is empowered by non-locality and non-Hermicity, providing new routes for controlling sound using the acoustic version of 2D materials.This review details the progress of non-local and non-Hermitian acoustic metasurfaces, providing an overview of the recent acoustic metasurface designs and discussing the critical role of non-locality and loss in acoustic metasurfaces. We further outline the synergy between non-locality and non-Hermiticity, and delineate the potential of using non-local and non-Hermitian acoustic metasurfaces as a new platform for investigating exceptional points (EPs), the hallmark of non-Hermitian physics. Finally, the current challenges and future outlook for this burgeoning field are discussed.

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Section: Non-hermitian Acoustics In Waveguides (1d)mentioning

confidence: 99%

Non-local and non-Hermitian acoustic metasurfaces

Wang,

Dong,

et al. 2023

Rep. Prog. Phys.

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“…One of the most intriguing developments in quantum mechanics over the past few decades has been the discovery of a non-Hermitian Hamiltonian ℋ that commutes with the parity-time (𝒫𝒯 ) operator, a property that leads to realenergy eigenvalues. [1][2][3] Recently, considerable efforts have been further motivated to investigate its classical analogy in photonics, [4][5][6][7][8][9][10][11][12] acoustics, [13][14][15][16][17][18][19][20][21][22][23] and many more areas [24][25][26][27] by means of interleaving balanced loss-gain regions. In contrast to the photonic gain that can be straightforwardly implemented in a locally controlled fashion through stimulated emission, which involves optical (electrical) pumping by an external source or via parametric processes, [28][29][30][31] no passive acoustic gain material exists in nature.…”

Section: Introductionmentioning

confidence: 99%

One-dimensional PT -symmetric acoustic heterostructure

Zhang¹,

Xiong²,

Cheng³

et al. 2022

Chinese Phys. B

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The explorations of parity-time ($\mathcal{PT}$)-symmetric acoustics have resided at the frontier in physics, and the pre-existing accessing of exceptional points typically depends on Fabry-Perot resonances of the coupling interlayer sandwiched between balanced gain and loss components. Nevertheless, the concise $\mathcal{PT}$-symmetric acoustic heterostructure, eliminating extra interactions caused by the interlayer, has not been researched in depth. Here we derive the generalized unitary relation for one-dimensional $\mathcal{PT}$-symmetric heterostructure of arbitrary complexity, and demonstrate four disparate patterns of anisotropic transmission resonances (ATRs) accompanied by corresponding spontaneous phase transitions. As a special case of ATR, the occasional bidirectional transmission resonance reconsolidates the ATR frequencies that split when waves incident from opposite directions, whose spatial profiles distinguish from a unitary structure. The derived theoretical relation can serve as a predominant signature for the presence of $\mathcal{PT}$ symmetry and $\mathcal{PT}$-symmetry-breaking transition, which may provide substantial support for the development of prototype devices with asymmetric acoustic responses.

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“…On account of this, there has been recently an intense surge of interest for active acoustic metamaterials, which could broadly enhance the real-world applicability of acoustic metamaterials by overcoming the challenges 29 . Active acoustic metamaterials have been widely put into use in various fields of acoustics and have played an important role, including acoustic gain 30 , parity-time symmetric acoustic metamaterials [31][32][33] , constant amplitude acoustic waves 34,35 , reconfigurable metasurfaces 36,37 , non-reciprocal meta-atoms [38][39][40][41][42][43] and topological metamaterials with external drive [44][45][46] . This indicates that active acoustic metamaterials hold significant promise and value for applications requiring lossless transmission.In this paper, we introduce the currently popular active acoustic material, carbon nanotube (CNT) film into a compact three-port acoustic device and achieve giant acoustic nonreciprocity by regulating the thermo-acoustic…”

mentioning

confidence: 99%

Total acoustic transmission in a honeycomb network empowered by compact acoustic isolator

Zhang

Bao

et al. 2023

Sci Rep

Self Cite

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In recent years, acoustic metamaterials have exhibited extraordinary potential for manipulating the propagation of sound waves. However, it has been a challenge to control the propagation of sound waves through arbitrary pathways in a network. In this work, we designed a compact three-port isolator that can produce giant acoustic nonreciprocity by introducing actively controlled CNT films to the device without altering the geometric symmetry of it. This concept is subsequently applied to construct a 4 × 7 honeycomb network, in which, total transmission of sound wave in arbitrary pathway can be slickly achieved. Unlike the acoustic topological insulator, which only supports total transmission of arbitrary pathway in the band gap, our method provides more degrees of freedom and can be realized at any frequency. This ability opens up a new method for routing sound waves and exhibits promising applications ranging from acoustic communication to energy transmission.

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Step-wise constant-amplitude waves in non-Hermitian disordered media

Cited by 5 publications

References 30 publications

Non-local and non-Hermitian acoustic metasurfaces

Non-local and non-Hermitian acoustic metasurfaces

One-dimensional PT -symmetric acoustic heterostructure

Total acoustic transmission in a honeycomb network empowered by compact acoustic isolator

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