Guo Jiamin, Gu Zhongming, Zhu Jie
Institute of Acoustics, School of Physics Science and Engineering, <a href="https://ror.org/03rc6as71">Tongji University</a>, Shanghai 200092, China.
Phys Rev Lett. 2024 Dec 6;133(23):236603. doi: 10.1103/PhysRevLett.133.236603.
Merging bound states in the continuum (BICs) has significant promise for wave manipulation since it can provide an ultrahigh Q factor when compared to the isolated BICs. However, the study of merging topological bound states in the continuum (TBICs) remains largely unexplored. In this Letter, we introduce a straightforward structure for crafting the merged higher order TBICs, i.e., the merged topological corner states in the continuum (MTCICs), via a synthetic way. Two identical topological insulators, supporting topological corner states within the bulk band, are mirror stacked. The eigenstates inherited from a single layer experience energy spectrum shifts without hybridization as interlayer couplings change, leading to the emergence of MTCICs. With acoustic crystals, we experimentally identify and characterize the MTCICs. The results evidently confirm the superior energy confinement capabilities of MTCICs over TBICs and gapped topological corner states (TCSs). Our Letter may deepen the understandings of both topological and BIC physics to inspire the development of devices with ultrahigh Q factor and enhanced robustness.
连续统中的合并束缚态（BICs）在波操控方面具有重大前景，因为与孤立的BICs相比，它能提供超高的品质因数。然而，对连续统中合并拓扑束缚态（TBICs）的研究在很大程度上仍未得到探索。在本信函中，我们通过一种合成方法引入了一种用于构建合并高阶TBICs（即连续统中的合并拓扑角态，MTCICs）的简单结构。两个相同的拓扑绝缘体，在体能带内支持拓扑角态，进行镜像堆叠。当层间耦合变化时，从单层继承的本征态经历能谱移动而无杂化，从而导致MTCICs的出现。利用声学晶体，我们通过实验识别并表征了MTCICs。结果明显证实了MTCICs相对于TBICs和带隙拓扑角态（TCSs）具有卓越的能量限制能力。我们的信函可能会加深对拓扑物理和BIC物理的理解，以推动具有超高品质因数和增强鲁棒性的器件的发展。
