Article
Physics, Multidisciplinary
Jean-Philippe Groby, Matthieu Mallejac, Aurelien Merkel, Vicente Romero-Garcia, Vincent Tournat, Daniel Torrent, Jensen Li
Summary: This work explores the closed forms of effective parameters in Willis materials through studying three asymmetric and reciprocal one-dimensional resonant configurations, demonstrating differences in coupling coefficients. The study highlights the way in which Willis coupling occurs in spatially asymmetric unit cells, as well as the absence of odd Willis coupling in reciprocal configurations. These findings are validated against experimental and numerical results in the three configurations, paving the way for novel physical understanding and engineering use of Willis acoustic materials.
NEW JOURNAL OF PHYSICS
(2021)
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
Physics, Multidisciplinary
Xinhua Wen, Heung Kit Yip, Choonlae Cho, Jensen Li, Namkyoo Park
Summary: We propose a concept called acoustic amplifying diode that combines signal isolation and amplification in a single device. The signal is exponentially amplified in one direction with no reflection and perfectly absorbed in another direction. By using impedance matching, the device eliminates reflection in both directions and prevents backscattering to the signal source. We demonstrate the amplifying diode using an active metamaterial with nonreciprocal Willis coupling, and discuss the flexibility of implementation with the presence of both reciprocal and nonreciprocal couplings.
PHYSICAL REVIEW LETTERS
(2023)
Article
Nanoscience & Nanotechnology
Zhujing Xu, Xingyu Gao, Jaehoon Bang, Zubin Jacob, Tongcang Li
Summary: The study explores the non-reciprocal energy transfer phenomenon caused by quantum vacuum fluctuations, demonstrating strong coupling between two micromechanical oscillators through modulation of Casimir interaction parameters, leading to non-reciprocal energy transfer.
NATURE NANOTECHNOLOGY
(2022)
Article
Acoustics
Rene Pernas-Salomon, Michael R. Haberman, Andrew N. Norris, Gal Shmuel
Summary: Materials with asymmetric microstructure can couple macroscopic fields from different physics, such as piezoelectric materials coupling mechanical and electric fields, and Willis materials anomalously coupling dynamic and elastic fields. Anomalous coupling between elastodynamic and electric fields emerges when piezoelectricity is incorporated into Willis materials. Our study elucidates the origins of this electromomentum coupling and provides insight for the future design of this new class of coupled-field metamaterials.
Article
Acoustics
Yu-Gui Peng, Yarden Mazor, Andrea Alu
Summary: The cross-coupling between strain and velocity in acoustic materials, known as Willis coupling, has gained increasing attention in acoustics. Willis coupling provides a new degree of freedom for controlling sound propagation and has enabled novel applications. This study explores the constraints and wave features in Willis media based on constitutive relations and the acoustic Poynting theorem. Additionally, a nonlocal model is proposed to uncover the relation between Willis media and nonlocal materials.
Article
Materials Science, Multidisciplinary
Hussein Esfahlani, Yarden Mazor, Andrea Alu
Summary: Metasurfaces are ultrathin planar arrays of carefully tailored subwavelength particles that enable agile and flexible manipulation of impinging waves. The application of Willis meta-atoms in acoustic metasurfaces offers additional knobs for manipulating and tailoring sound, providing full control of the impinging acoustic wave front. These nonperturbative phenomena in suitably tailored resonant scatterers have opened up exciting opportunities for exotic sound control.
Article
Multidisciplinary Sciences
Anis Maddi, Come Olivier, Gaelle Poignand, Guillaume Penelet, Vincent Pagneux, Yves Auregan
Summary: The authors present an efficient and nonreciprocal absorber for controlling sound based on thermoacoustic effect, which overcomes the limitations of conventional methods, especially at low frequencies.
NATURE COMMUNICATIONS
(2023)
Article
Acoustics
Zhanyu Li, Hongfei Qu, Hongkuan Zhang, Xiaoning Liu, Gengkai Hu
Summary: Acoustic Willis materials exhibit unconventional coupling between pressure and velocity, enabling extraordinary control over the propagation of acoustic waves. This study predicts the existence of interfacial modes at the interface between two acoustic Willis materials, dependent on the relative orientations of the coupling vectors. Experimental results confirm the theory, showing good agreement with simulations and theoretical analysis.
Article
Chemistry, Multidisciplinary
Ping Wang, Yu Wang, Hongcheng Zhou, Bing Li, Yifei Qin, Zhongming Yan
Summary: The paper proposes a high-efficiency transmissive polarization conversion metasurface (PCM) based on non-reciprocal metasurface integrated with NPN transistors. The PCM can convert input x- and y-polarized waves into y-polarized transmitted wave while eliminating the parasitic filtering effect. The total transmission efficiency of orthogonal polarizations is higher than 50% within 3.26-3.39 GHz, with a peak efficiency of 85.4% at 3.35 GHz. The proposed PCM also allows for expanding the range of received polarization states.
ADVANCED FUNCTIONAL MATERIALS
(2023)
Article
Multidisciplinary Sciences
Michel Fruchart, Ryo Hanai, Peter B. Littlewood, Vincenzo Vitelli
Summary: The article discusses the impact of non-reciprocity on the collective behavior of multi-body systems in out-of-equilibrium states, indicating that non-reciprocity leads to the emergence of time-dependent phases controlled by exceptional points. The article describes the non-reciprocal generalizations of three archetypal classes of self-organization out of equilibrium, including synchronization, flocking, and pattern formation.
Article
Acoustics
Steven R. Craig, Bohan Wang, Xiaoshi Su, Debasish Banerjee, Phoebe J. Welch, Mighten C. Yip, Yuhang Hu, Chengzhi Shi
Summary: We propose an active acoustic metamaterial with Willis coupling to significantly extend the tunability of effective density and bulk modulus. By using asymmetric feedback control circuits, the accessible parameter range is enlarged, making it applicable in various fields.
JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA
(2022)
Article
Physics, Multidisciplinary
Choonlae Cho, Xinhua Wen, Namkyoo Park, Jensen Li
Summary: This paper introduces a new type of Willis metamaterial that can precisely control acoustic waves and overcome the traditional limitations of passivity and reciprocity. By introducing independent kernels on a virtualized platform, artificial polarization is achieved, allowing for control of all four constitutive parameters.
COMMUNICATIONS PHYSICS
(2021)
Article
Physics, Multidisciplinary
Hongfei Qu, Xiaoning Liu, Anfu Zhang
Summary: The paper theoretically studies the unusual wave phenomena at interfaces between homogeneous acoustic Willis media, showing that Willis media provide more flexible control in wave front and energy flow when waves are transmitted through an interface. Unlike traditional acoustic fluids, Willis acoustic media support the existence of edge and interface waves, whose conditions and features are systematically investigated. The study reveals more possibilities for manipulating acoustic waves and may inspire new functional designs with acoustic Willis metamaterials.
FRONTIERS IN PHYSICS
(2023)
Article
Mechanics
Jintao Gu, Youheng Tang, Xiaole Wang, Zhenyu Huang
Summary: This paper investigates the sound insulation characteristics of plate-type acoustic metamaterials under practical conditions. The use of laminated plate-type acoustic metamaterials (LPAM) effectively isolates broadband low-frequency noise. Numerical studies and experiments confirm its superior sound insulation performance.
COMPOSITE STRUCTURES
(2022)