Observation of higher-order exceptional points in a non-local acoustic metagrating

Fang, Xinsheng; Gerard, Nikhil Jrk; Zhou, Zhiling; Ding, Hua; Wang, Nengyin; Jia, Bin; Deng, Yuanchen; Wang, Xu; Jing, Yun; Li, Yong

doi:10.1038/s42005-021-00779-x

Cited by 30 publications

(16 citation statements)

References 37 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This innate difference, therefore, renders the non-Hermitian concept even more intriguing in the acoustic platform. Mathematically, for any non-Hermitian system, the EP (of order n) exists as long as the Hamiltonian matrix, under a similarity transformation, can be shown to contain an n × n Jordan block J [133,134]…”

Section: The Minimal Modelmentioning

confidence: 99%

Non-local and non-Hermitian acoustic metasurfaces

Wang,

Dong,

et al. 2023

Rep. Prog. Phys.

Self Cite

View full text Add to dashboard Cite

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.

show abstract

Section: The Minimal Modelmentioning

confidence: 99%

Non-local and non-Hermitian acoustic metasurfaces

Wang,

Dong,

et al. 2023

Rep. Prog. Phys.

Self Cite

View full text Add to dashboard Cite

show abstract

“…In some recently proposed nonlocal metasurfaces, the effects of D and X are both considered. [15,21,39] Furthermore, when we compress unit-cell thickness to near zero, the manipulation ability brought by unit structure itself will disappear, and the nonlocal effect characterized by X plays a leading role. This condition can be expressed as…”

Section: Analysis Of the Ultrathin Holography Modelmentioning

confidence: 99%

“…Recently, some researchers are devoted to design different types of nonlocal metasurfaces, whose nonlocal responses are enhanced artificially thanks to the transverse coupling between adjacent unit cells. [15,21,39] However, these works are still difficult to get rid of structure limitation and reduce their thicknesses.…”

mentioning

confidence: 99%

Ultrathin Acoustic Holography

Liu

et al. 2023

Adv Materials Inter

View full text Add to dashboard Cite

How to realize acoustic holography via ultradeep‐subwavelength structures is a challenging problem in the past decades, which is thought impossible due to the linear proportional relationship between the structural thickness and acoustic wavelength. In this article, the methodology of ultrathin holography by patterning holes in an acoustic insulation plate with an ultradeep‐subwavelength thickness is introduced. The transmitted sound field can be manipulated arbitrarily to form a desired shape by designing the ultrathin pattern based on the nonlocal wave interaction theory. The physical mechanism of the nonlocal behavior to achieve a sophisticated hologram is revealed due to the interaction among the sound wave components themselves. Furthermore, the experiments are designed to map out the pressure amplitude field of a “sun” pattern in air and water, respectively. The work demonstrates the advantage of nonlocal ultrathin holography in the applications of ultrathin acoustic devices and provides inspiration for the holographic wave manipulation.

show abstract

“…In a waveguide structure, it is the degenerate point of the eigenvalues and corresponding eigenvectors of the scattering matrix [12,13]. EPs have received considerable widespread attention due to associated intriguing properties and exotic phenomena, such as unidirectional invisibility [14][15][16][17], laser mode selectivity [18,19], and enhanced sensitivity [11,[20][21][22][23].…”

Section: Introductionmentioning

confidence: 99%

Exceptional Points and Skin Modes in Non-Hermitian Metabeams

Cai

Jin

et al. 2022

Phys. Rev. Applied

Self Cite

View full text Add to dashboard Cite

We present a non-Hermitian metabeam exhibiting an exceptional point (EP) induced by enforcing parity-time (PT) symmetry through applied external forces. The EP is formed by the hybridization of two flexural wave modes and its output displacement is enhanced by attaching two pillars on top of the beam. The introduction of a tiny mass perturbation that breaks the PT symmetry leads to a splitting of the eigenfrequencies at the EP with a square-root dependence on the perturbation mass. This effect manifests itself in a splitting of resonant peaks in the frequency response. The enhanced sensitivity of the EP paves the way to the detection of small perturbations such as tiny masses and cracks. Another property of the metabeam is the existence of skin modes whose energies are localized at one end of the beam and can be generated by implementing nonreciprocal feedback interactions between the pillars. We demonstrate that the skin modes are broadband and independent of the excitation positions. From a practical perspective, we show the great potential of skin modes in broadband energy harvesting. Our study proposes approaches to manipulate the non-Hermitian elastic wave phenomena, paving the way for the development of highly sensitive sensors, vibration control, and energy harvesting.

show abstract

Observation of higher-order exceptional points in a non-local acoustic metagrating

Cited by 30 publications

References 37 publications

Non-local and non-Hermitian acoustic metasurfaces

Non-local and non-Hermitian acoustic metasurfaces

Ultrathin Acoustic Holography

Exceptional Points and Skin Modes in Non-Hermitian Metabeams

Contact Info

Product

Resources

About