Review
Physics, Applied
J. W. Rao, Y. T. Zhao, Y. S. Gui, X. L. Fan, D. S. Xue, C-M Hu
Summary: Dissipative coupling in a metamaterial structure leads to level attraction by cooperative radiation of resonators, supporting the coexistence of bound states in the continuum (BIC) and an antiresonance. By aligning BIC and antiresonance frequencies, control over the amplitude and phase of microwave transmission is achieved, resulting in a steep transition from complete extinction to nearly perfect transmission, accompanied by a phase jump indicative of slow light. Repurposing dissipation as a coupling mechanism opens up avenues for microwave sensing, switching, and realization of slow microwave.
PHYSICAL REVIEW APPLIED
(2021)
Article
Materials Science, Multidisciplinary
Haiyan Fan, He Gao, Tuo Liu, Shuowei An, Xianghong Kong, Guoqiang Xu, Jie Zhu, Cheng-Wei Qiu, Zhongqing Su
Summary: Non-Hermiticity in acoustic crystals leads to exotic topological phenomena and allows for manipulation of topological modes. Our work demonstrates an acoustic quadrupole topological insulator, offering a reconfigurable and versatile approach to manipulating topological phenomena.
Article
Physics, Applied
S. Puri, J. Ferdous, A. Shakeri, A. Basiri, M. Dubois, H. Ramezani
Summary: Researchers have proposed and tested a non-Hermitian acoustic superlattice that functions as a tunable precise filter, where the second sublattice's properties can be adjusted to absorb or reflect multiple frequencies with high accuracy.
PHYSICAL REVIEW APPLIED
(2021)
Article
Physics, Multidisciplinary
Francisco Correa, Luis Inzunza, Ian Marquette
Summary: A non-Hermitian generalisation of the Marsden-Weinstein reduction method is introduced to construct families of quantum PT-symmetric superintegrable models over an n-dimensional sphere S-n. The mechanism is illustrated with one-and two-dimensional examples, related to u(2) and u(3) Lie algebras respectively, providing new quantum models with real spectra and spontaneous PT-symmetric breaking. In certain limits, the models reduce to known non-Hermitian systems and complex extensions of previously studied real superintegrable systems.
JOURNAL OF PHYSICS A-MATHEMATICAL AND THEORETICAL
(2023)
Article
Multidisciplinary Sciences
Li Zhang, Yihao Yang, Yong Ge, Yi-Jun Guan, Qiaolu Chen, Qinghui Yan, Fujia Chen, Rui Xi, Yuanzhen Li, Ding Jia, Shou-Qi Yuan, Hong-Xiang Sun, Hongsheng Chen, Baile Zhang
Summary: The experimental realization of the non-Hermitian skin effect in a one-dimensional non-reciprocal acoustic crystal demonstrates unique features such as bipolar localization and Bloch point, revealing previously unnoticed characteristics of NHSE originating from complex non-Hermitian winding topology.
NATURE COMMUNICATIONS
(2021)
Article
Multidisciplinary Sciences
Denis Novitsky, Dmitry Lyakhov, Dominik Michels, Dmitrii Redka, Alexander A. Pavlov, Alexander S. Shalin
Summary: The study introduces a novel architecture driven by disordered loss-gain multilayers to control the passage time and wave-front shape of incident light, and allows for flexible tuning of output intensity through adjusting the level of disorder and utilizing nonlinear effects.
SCIENTIFIC REPORTS
(2021)
Article
Physics, Applied
Hilary M. Hurst, Benedetta Flebus
Summary: Non-Hermitian Hamiltonians provide an alternative framework for describing the dynamics of magnonic and hybrid magnonic systems, revealing important non-Hermitian physics phenomena in these systems.
JOURNAL OF APPLIED PHYSICS
(2022)
Article
Materials Science, Multidisciplinary
Haoshu Li, Shaolong Wan
Summary: The study reveals the existence of dynamic skin effect in non-Hermitian systems, caused by both non-Hermitian skin effect and Hermitian wave packet spreading. Unlike the uniform motion in Hermitian situations, the Gaussian wave packet in non-Hermitian systems can experience acceleration and amplification.
Article
Physics, Multidisciplinary
Cem Yuce
Summary: In a non-Hermitian lattice, eigenstates exhibit localization at an open edge due to the non-Hermitian skin effect. The study of quasi-stationary solutions and zero energy modes predicts a dramatically non-perturbative transition to eigenstates. The non-topological but robust characteristics of these modes are explored in a non-Hermitian variant of the Su-Schrieffer-Heeger (SSH) model.
Article
Materials Science, Multidisciplinary
Zixi Fang, Chen Fang, Kai Zhang
Summary: In this paper, we systematically investigate impurity-induced bound states in one-dimensional non-Hermitian systems. By constructing an impurity potential diagram, the minimal impurity potential required to generate bound states and the distribution of bound states are revealed. It is found that a finite impurity potential is required to generate bound states in the absence of Bloch saddle points.
Article
Physics, Multidisciplinary
Kai Zhang, Chen Fang, Zhesen Yang
Summary: In this study, the concept of dynamical degeneracy splitting is introduced to explain the anisotropic decay behaviors in non-Hermitian systems. It is shown that systems with dynamical degeneracy splitting exhibit frequency-resolved non-Hermitian skin effect and anomalous behavior in Green's function, resulting in uneven broadening in spectral function and anomalous scattering. The directional invisibility based on wave packet dynamics is proposed to investigate the geometry-dependent skin effect in higher dimensions. This work provides a guiding principle for exploring novel physical phenomena arising from the non-Hermitian skin effect.
PHYSICAL REVIEW LETTERS
(2023)
Article
Materials Science, Multidisciplinary
Kazuki Yokomizo, Shuichi Murakami
Summary: The non-Bloch band theory is applicable to energy bands in one-dimensional non-Hermitian systems. This theory can also be extended to higher-dimensional non-Hermitian systems by reducing them to one-dimensional non-Hermitian models. In this study, we apply the non-Bloch band theory to two classes of two-dimensional non-Hermitian systems and investigate their topological properties using the generalized Brillouin zone. We demonstrate the bulk-edge correspondence in the non-Hermitian Chern insulator model, showing a relationship between the Chern number defined from the generalized Brillouin zone and the presence of edge states.
Article
Materials Science, Multidisciplinary
Kohei Kawabata, Ken Shiozaki, Shinsei Ryu
Summary: This article discusses the existence of intrinsic non-Hermitian topological phases in one dimension under many-body interactions, constructing a many-body topological invariant through the winding of the complex-valued many-body spectrum.
Article
Optics
Lingxuan Zhang, Lei Ying, Li Ge, Wei Zhao, Wenfu Zhang
Summary: The study reports the phenomenon of fast forward and backward light pulse propagation in effectively transparent non-Hermitian photonic systems, identifying a critical point near an exceptional point that displays a diverging dispersion. Superluminal light pulse propagation is found on the two sides of the critical point, and can be understood by a conservation relation of group velocities. The abrupt transition between fast forward and backward light can be tuned, potentially allowing for detecting atom-scale movement of the waveguides with little time delay.
LASER & PHOTONICS REVIEWS
(2021)
Article
Materials Science, Multidisciplinary
Hamed Ghaemi-Dizicheh
Summary: In this paper, a universal approach is presented to study the transport of tight-binding platforms in non-Hermitian nonreciprocal systems. The conditions for transport effects such as reflectionless and transparent transport, lasing, and coherent perfect absorption are identified using a generalized transfer matrix method. The analysis covers higher-dimensional models and those with an internal degree of freedom, going beyond the previously studied one-dimensional chains.
Article
Physics, Applied
He Gao, Zhongming Gu, Shanjun Liang, Tuo Liu, Jie Zhu, Zhongqing Su
Summary: This study presents an auxiliary ultrasound focusing meta-lens for effective sound energy transmission and beam manipulation through stiff and dense materials. The meta-lens significantly enhances ultrasound transmission and focusing without the need for through holes or openings. The simple meta-structures are designed and optimized using a genetic algorithm. The meta-lens shows great application prospects in medical imaging and disease treatment.
APPLIED PHYSICS LETTERS
(2022)
Article
Engineering, Mechanical
Shuowei An, Tuo Liu, Haiyan Fan, He Gao, Zhongming Gu, Shanjun Liang, Sibo Huang, Yi Zheng, Yafeng Chen, Li Cheng, Jie Zhu
Summary: This study proposes a second-order elastic topological insulator (SETI) with valley-selective topological corner states, which can be activated by engineering the valley positions. Experimental results validate the existence of valley-selective corner states and the anti-symmetric displacement profile. This research provides a new approach for the flexible manipulation of elastic waves and has potential applications in various fields.
INTERNATIONAL JOURNAL OF MECHANICAL SCIENCES
(2022)
Article
Engineering, Mechanical
Haiyan Fan, He Gao, Shuowei An, Zhongming Gu, Shanjun Liang, Yi Zheng, Tuo Liu
Summary: The study investigates the experimental demonstration of topological edge states in elastic metamaterials described by the Su-Schrieffer-Heeger model under both Hermitian and non-Hermitian conditions. By altering hopping strengths and absorptive dampings, non-trivial and trivial band gaps along with the associated topological edge states were achieved. These results extend the topological physics in elastic wave systems beyond the traditional assumption of Hermiticity.
MECHANICAL SYSTEMS AND SIGNAL PROCESSING
(2022)
Article
Multidisciplinary Sciences
Tuo Liu, Shuowei An, Zhongming Gu, Shanjun Liang, He Gao, Guancong Ma, Jie Zhu
Summary: This study demonstrates the control of acoustic vortex generation by controlling the on-off states of two coherent monopolar sources, achieving switchable OAM without system reconfiguration. It offers new opportunities for chiral sound manipulation and tunable acoustic OAM devices.
Article
Mechanics
Xudong Tian, Tuo Liu, Tiantian Wang, Jie Zhu, Chihyung Wen
Summary: In this study, an acoustic metasurface made of two layers of perforated plates is proposed for suppressing the Mack second mode in hypersonic boundary-layer flow. By adjusting the hole structure and impedance phase of the two layers, the metasurface achieves both acoustic wave permeability and suppression effect, providing a new design strategy for hypersonic boundary-layer stabilization.
Article
Multidisciplinary Sciences
Xiaoxiao Wu, Haiyan Fan, Tuo Liu, Zhongming Gu, Ruo-Yang Zhang, Jie Zhu, Xiang Zhang
Summary: This article reports an approach for topological phononics, utilizing the unique interplay of sound in different media. The authors demonstrate the realization of type-II nodal rings in a simple three-dimensional phononic crystal and experimentally observe strongly tilted drumhead surface states. This phononic approach opens up new possibilities for exploring topological physics in classical systems and designing high-performance acoustic devices.
NATURE COMMUNICATIONS
(2022)
Article
Physics, Applied
Lei Fan, Yafeng Chen, Shuowei An, Tuo Liu, Haiyan Fan, Jie Zhu, Zhongqing Su
Summary: A second-order elastic topological insulator (SETI) is created by etching a series of C-shaped slots on a metal plate, achieving dual-band topological corner states. The etched slots act as cantileverlike oscillators that couple with the flexural vibration modes of the plate, resulting in multiple locally resonant band gaps. The configuration of these slots on a C4v-symmetric lattice enables the creation of topologically distinct metastructures. The observation of the dual-band corner states in two broad topological band gaps simplifies the fabrication of metastructures for implementing locally resonant elastic topological insulators, benefiting applications such as elastic wave trapping and energy amplification at subwavelength scale.
PHYSICAL REVIEW APPLIED
(2023)
Article
Materials Science, Multidisciplinary
Haiyan Fan, He Gao, Tuo Liu, Shuowei An, Xianghong Kong, Guoqiang Xu, Jie Zhu, Cheng-Wei Qiu, Zhongqing Su
Summary: Non-Hermiticity in acoustic crystals leads to exotic topological phenomena and allows for manipulation of topological modes. Our work demonstrates an acoustic quadrupole topological insulator, offering a reconfigurable and versatile approach to manipulating topological phenomena.
Article
Materials Science, Multidisciplinary
Haiyan Fan, He Gao, Shuowei An, Zhongming Gu, Yafeng Chen, Sibo Huang, Shanjun Liang, Jie Zhu, Tuo Liu, Zhongqing Su
Summary: This study demonstrates experimentally the generation of topological edge states in the continuum solely through non-Hermiticity, without additional coupling modulation, in a one-dimensional trimerized elastic lattice. Appropriately tailored non-Hermitian modulation can induce topological edge states that appear in the bulk spectrum, and their existence is closely linked to the configurations of the lattice boundaries.
Article
Materials Science, Multidisciplinary
He Gao, Haoran Xue, Zhongming Gu, Linhu Li, Weiwei Zhu, Zhongqing Su, Jie Zhu, Baile Zhang, Y. D. Chong
Summary: This study introduces a variant of the non-Hermitian skin effect, called the anomalous Floquet NHSE, achieved by fixed on-site gain or loss in a one-dimensional coupled ring resonator lattice. The experimental implementation in an acoustic lattice shows good agreement with theoretical predictions, with a broadband asymmetric transmission achieved with a relative bandwidth of around 40%.
Article
Acoustics
Yi Zheng, Shanjun Liang, Haiyan Fan, Shuowei An, Zhongming Gu, He Gao, Tuo Liu, Jie Zhu
Summary: This letter presents the design and experimental demonstration of a gradient metasurface guiding spoof surface acoustic waves (SSAWs) in the manner of a Luneburg lens for sound. By correlating the propagation characteristics of SSAWs with the effective surface acoustic impedance, a straightforward concentric surface structure design is proposed to realize the required refractive index distribution. The results from both simulation and measurement show that grazing incident sound is converted into SSAWs propagating along the metasurface and focusing on the edge of the opposite side of the lens, which may find applications in direction detection and acoustic sensing.
JASA EXPRESS LETTERS
(2022)
