Design and Robustness Evaluation of Valley Topological Elastic Wave Propagation in a Thin Plate with Phononic Structure
Design and Robustness Evaluation of Valley Topological Elastic Wave Propagation in a Thin Plate with Phononic Structure
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DOI：
10.3390/sym14102133
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发表时间：
2022-10
期刊：
影响因子：
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通讯作者：
Motoki Kataoka;Masaaki Misawa;K. Tsuruta
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文献类型：
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作者：
Motoki Kataoka;Masaaki Misawa;K. Tsuruta
基于声子色散中的能带拓扑概念，我们设计了一种薄板拓扑声子晶体，用于研制高效的弹性波导。尽管各种拓扑声子结构已被积极地提出，声子带的定量设计策略及其在弹性制度下的鲁棒性评估仍然缺失，阻碍了拓扑声学器件的实现。我们采用雪花状结构的晶体晶胞，并确定了最佳的结构，表现出拓扑相变的平面声子晶体的晶胞结构的变化。带隙宽度可以通过改变雪侧分支的长度来调节，并且在具有三重旋转对称性的单胞结构中发生了拓扑相变。设计了基于不同能带拓扑晶体界面边缘模的弹性波导，并对其传输效率进行了数值和实验研究。结果表明，弹性波在薄板中传播的鲁棒性。此外，我们实验估计的后向散射长度，这措施的鲁棒性的拓扑保护的传播状态对结构的不均匀性。结果定量地表明，对后向散射的免疫退化主要发生在波导中的角落，表明观察到的边缘模式是一个相对较弱的拓扑状态。
Based on the concept of band topology in phonon dispersion, we designed a topological phononic crystal in a thin plate for developing an efficient elastic waveguide. Despite that various topological phononic structures have been actively proposed, a quantitative design strategy of the phononic band and its robustness assessment in an elastic regime are still missing, hampering the realization of topological acoustic devices. We adopted a snowflake-like structure for the crystal unit cell and determined the optimal structure that exhibited the topological phase transition of the planar phononic crystal by changing the unit cell structure. The bandgap width could be adjusted by varying the length of the snow-side branch, and a topological phase transition occurred in the unit cell structure with threefold rotational symmetry. Elastic waveguides based on edge modes appearing at interfaces between crystals with different band topologies were designed, and their transmission efficiencies were evaluated numerically and experimentally. The results demonstrate the robustness of the elastic wave propagation in thin plates. Moreover, we experimentally estimated the backscattering length, which measures the robustness of the topologically protected propagating states against structural inhomogeneities. The results quantitatively indicated that degradation of the immunization against the backscattering occurs predominantly at the corners in the waveguides, indicating that the edge mode observed is a relatively weak topological state.