南京大学合作团队:设计和研制了三维拓扑声子晶体
作者:Cheng He, Si-Yuan Yu, Hao Ge, Huaiqiang Wang, Yuan Tian, Haijun Zhang, Xiao-Chen Sun, Y. B. Chen, Jian Zhou, Ming-Hui Lu, Yan-Feng Chen
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2018-11-07 22:38:37
南京大学何程、卢明辉和陈延峰研究团队与张海军课题组合作,在理论上设计和研制了三维拓扑声子晶体。研究组利用声学微腔构造了由双层六角晶格堆砌而成的三维声子晶体,通过引入滑移对称性,破缺了z和x方向镜面对称性,形成全方向带隙;而原来四重简并点也破缺成两个两重简并,该两重简并受滑移对称性保护,在特定方向上满足赝时间反演对称性,从而可用于实现空气纵声波的赝自旋以及赝自旋-能谷耦合表面态。通过精确选择结构参数并通过3D打印技术制备了三维拓扑声子晶体。这个工作的重要意义在于:1)首次提出并在实验上实现了三维拓扑声子晶体中的赝自旋-能谷耦合表面态,有望应用于声传播调控和降噪隔声等领域;2)实现了多方向且各向异性可控的声拓扑表面传输特性,它更接近实际应用;3)提出了一种利用纵声波构造全矢量声赝自旋的方案,未来有望开发并应用于声赝自旋器件。
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Three-dimensional topological acoustic crystals with pseudospin-valley coupled saddle surface states
作者:Cheng He, Si-Yuan Yu, Hao Ge, Huaiqiang Wang, Yuan Tian, Haijun Zhang, Xiao-Chen Sun, Y. B. Chen, Jian Zhou, Ming-Hui Lu, Yan-Feng Chen
●
2018-11-07 22:38:37
导语
Topological valley states at the domain wall between two artificial crystals with opposite valley Chern numbers offer a feasible way to realize robust wave transport since only broken spatial symmetry is required. In addition to the valley, spin and crystal dimension are two other important degrees of freedom, particularly in realizing spin-related topological phenomena. Here we experimentally demonstrate that it is possible to construct two-dimensional acoustic topological pseudospin-valley coupled saddle surface states, designed from glide symmetry in a three-dimensional system. By taking advantage of such two-dimensional surface states, a full set of acoustic pseudospins can be realized, exhibiting pseudospin-valley dependent transport. Furthermore, due to the hyperbolic character of the dispersion of saddle surface states, multi-directional anisotropic controllable robust sound transport with little backscattering is observed. Our findings may open research frontiers for acoustic pseudospins and provide a satisfactory platform for exploring unique acoustic topological properties in three-dimensional structures.
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