声学超构材料中的拓扑态研究

Acoustic topological state is one of the hottest research topic in acoustics field. The transmission of topological states is unidirectional, back scattering inhibited and immune to the defects. It is expected to have extensive application in acoustic information transport system. Until now, most research works focused on the acoustic topological states in phononic crystals. The mechanism of topological states is the Bragg scattering of scatterers. Another typical acoustic artificial structure is the acoustic metamaterial. It has subwavelength band structure, which is due to the local resonance of scatterer itself. And in subwavelength, acoustic metamaterial has negative effective medium parameters. However the research about acoustic topological states in acoustic metamaterials is very few. In this proposal, based on our initial research work, we plan to develop theoretical, simulated, experimental research work about acoustic topological states in acoustic metamaterials. We plan to demonstrate the mechanism of the appearance of acoustic topological states in subwavelength region, investigate the relationship between local resonance, effective medium and topology of band, achieve topological robust unidirectional transmission in subwavelength region. Our proposal expand the acoustic topological states to subwavelength region, achieve miniaturization of acoustic topological device. The research in our proposal has rich physical connotation and wide application prospect.

声学拓扑态是近年来声学领域的研究热点之一，它的传播具有单向性、背散射抑制和对缺陷散射免疫的优秀性质，在声学信息传输领域具有广泛的潜在应用价值。目前大部分声学拓扑态的研究工作都集中在声子晶体中，它的产生决定于晶体中散射体对声波的布拉格散射。另一种典型的声学人工晶体是声学超构材料，它能产生亚波长波段的能带，其物理机制来源于散射体单体的局域共振，并且亚波长下材料具有负的等效介质参数。而声学超构材料中拓扑态的研究还非常少。本项目在前期研究工作的基础上，拟从理论计算、数值模拟和实验验证三个方面，深入开展声学超构材料中的声学拓扑态的研究，阐明亚波长波段声学拓扑态产生的物理机理，探究局域共振机制、等效介质参数与能带拓扑性质的关系，实现亚波长波段声学拓扑态的鲁棒性的单向传输。本项目将声学拓扑态的工作波长拓展到亚波长范围，实现了声学拓扑材料的小型化，具有丰富的物理内涵和广阔的应用前景。

本项目主要研究包含局域共振单元的声子晶体中的拓扑态，通过构建理论模型，解析计算声子晶体的能带，并通过数值模拟验证理论结果，分析各种物理参数对能带影响，计算能带的拓扑不变量，调节参数实现能带的拓扑反转，将不同拓扑性质的声子晶体拼接在一起，在界面上实现声学拓扑态。最后通过实验测量，验证理论和模拟的结果。通常的声学拓扑态是出现在Bragg禁带中，本项目的研究成果可实现声学拓扑态在亚波长波段出现，对声学器件的小型化具有重大的应用价值。除此之外，本项目还支持了其他与声学拓扑态相关的研究，在本项目的支持下一共发表SCI论文7篇，获批1项发明专利。