Elastic wave absorption at subwavelength scale is of significance in many engineering applications.Non-Hermitian metamaterials show the ability in high-efficiency wave absorption.However,the single functionality of me...Elastic wave absorption at subwavelength scale is of significance in many engineering applications.Non-Hermitian metamaterials show the ability in high-efficiency wave absorption.However,the single functionality of metamaterials is an important limitation on their practical applications for lack of tunability and reconfigurability.Here,we propose a tunable and reconfigurable non-Hermitian piezoelectric metamaterial bar,in which piezoelectric bars connect with resonant circuits,to achieve asymmetric unidirectional perfect absorption(UPA)and symmetric bidirectional perfect absorption(PA)at low frequencies.The two functions can be arbitrarily switched by rearranging shunted circuits.Based on the reverberation-ray matrix(RRM)method,an approach is provided to achieve UPA by setting an exceptional point(EP)in the coupled resonant bandgap.By using the transfer matrix method(TMM)and the finite element method(FEM),it is observed that a non-Hermitian pseudo-band forms between two resonant bandgaps,and the EP appears at the bottom of the pseudo-band.In addition,the genetic algorithm is used to accurately and efficiently design the shunted circuits for desired low-frequency UPA and PA.The present work may provide new strategies for vibration suppression and guided waves manipulation in wide potential applications.展开更多
The interaction between cavity field and atoms plays an important role in exploring the abundant non-Hermitian physics and constructing powerful wave function devices.In this work,we propose theoretically and realize ...The interaction between cavity field and atoms plays an important role in exploring the abundant non-Hermitian physics and constructing powerful wave function devices.In this work,we propose theoretically and realize experimentally unidirectional perfect absorption in a non-Hermitian acoustic system with the help of the topological bound state in the continuum(BIC),which is established by the hybrid interaction between one trivial BIC and another conventional resonant state.In the 2D parameter space spanned by frequency and distance between the two resonators,the topological scattering singularities appear in pairs and are associated with topological distinguished charges.Meanwhile,we reveal the origin of topological charges and their continuous evolution with the loss factor.At a specific loss factor,two topological charges just annihilate together,and acoustic perfect absorption induced by topological BIC is realized at the left incidence,while there is no phase singularity and near-total reflection is observed at the right incidence,hence the system presents extreme asymmetry.Our work bridges the gap between scattering characteristics of non-Hermitian acoustic systems and topological scattering singularities,which may contribute to the research of novel non-Hermitian physics and the practical applications of advanced absorbers and sensors.展开更多
基金the National Natural Science Foundation of China(Nos.11991033 and 11890681)。
文摘Elastic wave absorption at subwavelength scale is of significance in many engineering applications.Non-Hermitian metamaterials show the ability in high-efficiency wave absorption.However,the single functionality of metamaterials is an important limitation on their practical applications for lack of tunability and reconfigurability.Here,we propose a tunable and reconfigurable non-Hermitian piezoelectric metamaterial bar,in which piezoelectric bars connect with resonant circuits,to achieve asymmetric unidirectional perfect absorption(UPA)and symmetric bidirectional perfect absorption(PA)at low frequencies.The two functions can be arbitrarily switched by rearranging shunted circuits.Based on the reverberation-ray matrix(RRM)method,an approach is provided to achieve UPA by setting an exceptional point(EP)in the coupled resonant bandgap.By using the transfer matrix method(TMM)and the finite element method(FEM),it is observed that a non-Hermitian pseudo-band forms between two resonant bandgaps,and the EP appears at the bottom of the pseudo-band.In addition,the genetic algorithm is used to accurately and efficiently design the shunted circuits for desired low-frequency UPA and PA.The present work may provide new strategies for vibration suppression and guided waves manipulation in wide potential applications.
基金supported by the National Key Research and Development Program of China(Grant No.2021YFA1400602)the National Natural Science Foundation of China(Grant Nos.12074286,and 12004284)+3 种基金the Shanghai Science and Technology Committee(Grant No.21JC1405600)the Fundamental Research Funds for the Central Universities(Grant No.22120210579)the Chenguang Program of Shanghai Education Development Foundationthe Shanghai Municipal Education Commission(Grant No.21CGA22)。
文摘The interaction between cavity field and atoms plays an important role in exploring the abundant non-Hermitian physics and constructing powerful wave function devices.In this work,we propose theoretically and realize experimentally unidirectional perfect absorption in a non-Hermitian acoustic system with the help of the topological bound state in the continuum(BIC),which is established by the hybrid interaction between one trivial BIC and another conventional resonant state.In the 2D parameter space spanned by frequency and distance between the two resonators,the topological scattering singularities appear in pairs and are associated with topological distinguished charges.Meanwhile,we reveal the origin of topological charges and their continuous evolution with the loss factor.At a specific loss factor,two topological charges just annihilate together,and acoustic perfect absorption induced by topological BIC is realized at the left incidence,while there is no phase singularity and near-total reflection is observed at the right incidence,hence the system presents extreme asymmetry.Our work bridges the gap between scattering characteristics of non-Hermitian acoustic systems and topological scattering singularities,which may contribute to the research of novel non-Hermitian physics and the practical applications of advanced absorbers and sensors.