Efficient nonreciprocal mode transitions in spatiotemporally modulated acoustic metamaterials

Authors

• Zhaoxian Chen, Department of Physics, Nanjing University, People’s Republic of China
• Yugui Peng, CUNY Advanced Science Research Center
• Haoxiang Li, Department of Physics, Nanjing University, People’s Republic of China
• Jingjing Liu, Department of Physics, Nanjing University, People’s Republic of China
• Yujiang Ding, Department of Physics, Nanjing University, People’s Republic of China
• Bin Liang, Department of Physics, Nanjing University, People’s Republic of China
• Xue-Feng Zhu, School of Physics and Innovation Institute, Huazhong University of Science and Technology, Wuhan, Hubei, People’s Republic of China
• Yanqing Lu, College of Engineering and Applied Sciences, Nanjing University, People’s Republic of China
• Jianchun Cheng, Department of Physics, Nanjing University, People’s Republic of China
• Andrea Alù, CUNY Advanced Science Research CenterFollow

Document Type

Article

Publication Date

2021

Abstract

In linear, lossless, time-invariant, and nonbiased acoustic systems, mode transitions are time reversible, consistent with Lorentz reciprocity and implying a strict symmetry in space-time for sound manipulation. Here, we overcome this fundamental limitation by implementing spatiotemporally modulated acoustic metamaterials that support nonreciprocal sound steering. Our mechanism relies on the coupling between an ultrathin membrane and external biasing electromagnetic fields, realizing programmable dynamic control of the acoustic impedance over a motionless and noiseless platform. The fast and flexible impedance modulation of our metamaterial imparts an effective unidirectional momentum in space-time to realize nonreciprocal transitions in k-ω space between different diffraction modes. On the basis of these principles, we demonstrate efficient nonreciprocal sound steering, showcasing unidirectional evanescent wave conversion and nonreciprocal upconversion focusing. More generally, our metamaterial platform offers opportunities for generation of nonreciprocal Bloch waves and extension to other domains, such as non-Hermitian topological and parity-time symmetric acoustics.

Comments

This article was originally published in Science Advances, available at http://dx.doi.org/10.1126/sciadv.abj1198

This work is distributed under a Creative Commons Attribution-NonCommercial 4.0 International License (CC BY-NC 4.0).