Topological Creation of Acoustic Pseudospin Multipoles in a Flow-Free Symmetry-Broken Metamaterial Lattice
Topological Creation of Acoustic Pseudospin Multipoles in a Flow-Free Symmetry-Broken Metamaterial Lattice
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无流对称破缺超材料晶格中声学赝自旋多极子的拓扑创建
DOI：
10.1103/physrevlett.118.084303
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发表时间：
2017-02-23
影响因子：
8.6
通讯作者：
Liu, Xiaojun
中科院分区：
文献类型：
--
作者：
Zhang, Zhiwang;Wei, Qi;Liu, Xiaojun
拓扑声学的发现彻底改变了声音传播的基本概念，产生了引人注目的不受散射影响的非常规声学边缘模式。由于声音的无自旋特性，对声学系统拓扑状态至关重要的“自旋”自由度通常是通过循环背景流或预设耦合谐振器环形波导来实现的，这大大增加了工程的复杂性。在这里，我们实现了一个简单的无流动对称破缺的超材料晶格中的声学伪自旋多极态，其中每个超分子内的顺时针（逆时针）声音传播模拟了伪自旋向下（伪自旋向上）。我们证明了通过简单地收缩或扩展超分子来调节分子间耦合的强度可以诱导赝自旋偶极子和四极子之间的能带反转效应，从而导致拓扑相变。进一步论证了拓扑保护边缘状态和可重构的拓扑单向声传输。这些结果为构建具有多种用途的新型声学拓扑绝缘体提供了多种途径。
The discovery of topological acoustics has revolutionized fundamental concepts of sound propagation, giving rise to strikingly unconventional acoustic edge modes immune to scattering. Because of the spinless nature of sound, the "spinlike" degree of freedom crucial to topological states in acoustic systems is commonly realized with circulating background flow or preset coupled resonator ring waveguides, which drastically increases the engineering complexity. Here we realize the acoustic pseudospin multipolar states in a simple flow-free symmetry-broken metamaterial lattice, where the clockwise (anticlockwise) sound propagation within each metamolecule emulates pseudospin down (pseudospin up). We demonstrate that tuning the strength of intermolecular coupling by simply contracting or expanding the metamolecule can induce the band inversion effect between the pseudospin dipole and quadrupole, which leads to a topological phase transition. Topologically protected edge states and reconfigurable topological one-way transmission for sound are further demonstrated. These results provide diverse routes to construct novel acoustic topological insulators with versatile applications.