Structural periodicity dependent scattering behavior in parity-time symmetric elastic metamaterials

Yi, Jianlin; Ma, Zhaoyang; Xia, Rongyu; Negahban, Mehrdad; Chen, Chang; Li, Zheng

doi:10.1103/physrevb.106.014303

Cited by 21 publications

(6 citation statements)

References 51 publications

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“…Besides first-order elastic TIs [13][14][15][16][17][18], HOTIs have also been explored in elastic wave systems [8,[19][20][21][22][23][24] to manipulate mechanical energy transfer and information transmission [25,26]. Typical examples include the development of new technologies and device for vibration control [21,27,28], information processing [29], and analog computation [30], among others. The multipole moment model [8] and the generalized Su-Schrieffer-Heeger (SSH) model [19] have been used to construct elastic HOTIs.…”

Section: Introductionmentioning

confidence: 99%

Delocalization and higher-order topology in a nonlinear elastic lattice

Yi,

Chen

2024

New J. Phys.

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Topological elastic waves provide novel and robust ways for manipulating mechanical energy transfer and information transmission, with potential applications in vibration control, analog computation, and more. Recently discovered higher-order topological insulators (HOTIs) with multidimensional and hierarchical edge states can further expand the capabilities of topological elastic waves. However, the effects of nonlinearity on elastic HOTIs remain elusive. In this paper, we propose a nonlinear elastic higher-order topological Kagome lattice. After briefly reviewing its linear properties, we explore the effects of nonlinearity on the higher-order band topology and topological states. To do this, we have developed a method to calculate approximate nonlinear modes in order to identify the bulk polarization and probe the higher-order topological phase in the nonlinear lattice. We find that nonlinearity induces unusual delocalization of topological corner states, band crossing, and higher-order topological phase transition. The delocalization reveals that intracell hardening nonlinearity leads to direct delocalization of topological corner states while intracell softening nonlinearity first enhances and then reduces localization. The nonlinear higher-order topological phase is amplitude dependent, and we demonstrate a transition from a trivial to a non-trivial phase, enabling amplitude induced topological corner and edge states. Additionally, this phase transition corresponds to the closing and reopening of the bandgap, accompanied by an unusual band crossing. By examining the band topology before and after the band crossing, we find that the bulk polarization becomes quantized with respect to amplitude and can predict higher-order topological phases in nonlinear lattices. The obtained results are expected to be beneficial for the development of tunable and robust elastic wave devices.

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Section: Introductionmentioning

confidence: 99%

Delocalization and higher-order topology in a nonlinear elastic lattice

Yi,

Chen

2024

New J. Phys.

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“…and solids [105], where the refractive index is determined by n = c/c 0 (c and c 0 being wave speed in the meta-unit and background medium). More explicitly, since c are determined by the two constitutive terms, i.e.…”

Section: Introduction Of Non-hermitian Acousticsmentioning

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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“…Metamaterials have been widely investigated by artificially designing their microstructures for achieving highly unusual properties in elastic wave propagations, like broadening the passband [7] or bandgap [8], cloaking wave [9], negative refraction [10], and one-way wave transport [11]. Recently, non-Hermitian metamaterials with loss or/and gain, as open systems, have attracted a lot of attention because the viscosity loss is ubiquitous in natural materials, and more importantly, it has been forming non-Hermitian metamaterials to realize special wave phenomena, such as the skin effect [12], asymmetric mode switching [13], Bloch oscillations [14], and coherent perfect absorption using lasers [15]. The existence of the exceptional point (EP) in non-Hermitian systems is significant for realizing fascinating phenomena of wave propagation.…”

Section: Introductionmentioning

confidence: 99%

“…Piezoelectric metamaterials are conveniently and accurately tunable because their shunted external circuits can be highly designable and controllable to change the effective mechanical parameters [22][23][24]. Based on piezoelectric metamaterials, Yi et al [15] proposed reconfigurable metamaterials to design a coherent perfect absorber for longitudinal and flexural waves, Chen et al [25] designed a metabeam to realize the tunable UZR of a flexural wave, and Katerina et al [26] proposed a non-Hermitian metasurface for unidirectional focusing of flexural waves. However, these researches are only focused on numerical simulation, and there is still a lack of the corresponding experimental study for the tunable EP and UZR based on piezoelectric metamaterials.…”

Section: Introductionmentioning

confidence: 99%

Versatile non-Hermitian piezoelectric metamaterial beam with tunable asymmetric reflections

Xia

et al. 2022

Front. Phys.

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Non-Hermitian systems have been widely utilized to achieve specific functions for manipulating abnormal wave motion, such as asymmetric mode switching, unidirectional zero reflection (UZR), and unidirectional perfect absorption (UPA). In this paper, a novel non-Hermitian piezoelectric metamaterial beam is proposed to realize the tunable UZR of flexural waves. The unit cell of this non-Hermitian metamaterial beam consists of a host beam and two pairs of piezoelectric patches shunting different resistor–inductor circuits. Based on the flexural wave theory, the transfer matrix method is introduced to analyze the influence of electrical boundary conditions on the UZR and further clarify the relationship between the UZR and the exceptional point. The exceptional point depends only on the dissipative circuit, and it has no need for the balanced gain and loss like parity–time symmetric metamaterial. Furthermore, the UZR for the desired frequency is realized by applying a genetic algorithm, and its effectivity is experimentally validated. In addition, the non-Hermitian metamaterial beam is designed to realize the UPA of flexural waves. Results indicate that the proposed metamaterial beam is versatile and can achieve tunable manipulations of asymmetric wave propagations and has widely promising applications in many fields, such as non-destructive testing, enhanced sensing, wave isolation and vibration attenuation.

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Structural periodicity dependent scattering behavior in parity-time symmetric elastic metamaterials

Cited by 21 publications

References 51 publications

Delocalization and higher-order topology in a nonlinear elastic lattice

Delocalization and higher-order topology in a nonlinear elastic lattice

Non-local and non-Hermitian acoustic metasurfaces

Versatile non-Hermitian piezoelectric metamaterial beam with tunable asymmetric reflections

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