论文标题
二维Xenes和配体功能化衍生物的Phononic Stiefel-Whitney拓扑用角振动模式
Phononic Stiefel-Whitney topology with corner vibrational modes in two-dimensional Xenes and ligand-functionalized derivatives
论文作者
论文摘要
二维（2D）Stiefel-Whitney（SW）绝缘子是一种脆弱的拓扑状态，其特征是在时空反转对称性的情况下第二个SW类。到目前为止，已经在几种电子材料中提出了SWIS，但在语音系统中很少提出。在这里，我们认识到，一大群2D屈曲的蜂窝晶体称为Xenes，它们的配体功能化衍生物实现了非平凡的语音SW拓扑结构。语音SWIS通过非零第二SW数字$ W_2 = 1 $识别，与张别的边缘状态和健壮的拓扑角模式相关联。尽管这些材料中电子拓扑特性具有多功能性，但非平凡的语音SW拓扑主要归因于由于蜂窝状lattice的结构性屈曲，因此平面内声学和平面外光学带之间的双带反转。我们的发现不仅揭示了2D Xene相关材料的语音拓扑特性，而且还提供了具有简单的语音光谱的丰富合成材料候选物，用于对语音SW拓扑物理学的进一步实验研究。
Two-dimensional (2D) Stiefel-Whitney (SW) insulator is a fragile topological state characterized by the second SW class in the presence of space-time inversion symmetry. So far, SWIs have been proposed in several electronic materials but seldom in phononic systems. Here we recognize that a large class of 2D buckled honeycomb crystals termed Xenes and their ligand-functionalized derivatives realize the nontrivial phononic SW topology. The phononic SWIs are identified by a nonzero second SW number $w_2=1$, associated with gaped edge states and robust topological corner modes. Despite the versatility of electronic topological properties in these materials, the nontrivial phononic SW topology is mainly attributed to the double band inversion between in-plane acoustic and out-of-plane optical bands with opposite parities due to the structural buckling of the honeycomb lattice. Our findings not only reveal an overlooked phononic topological property of 2D Xene-related materials, but also afford abundant readily synthesizable material candidates with simple phononic spectra for further experimental studies of phononic SW topology physics.
