npj: 高阶拓扑绝缘体—磁涡旋集体振荡涌现拓扑角态

来源：知社学术圈

在各类系统中寻找和发现拓扑相和拓扑材料是当前物质科学和材料工程学的一个核心问题。近年来，一类全新的拓扑态-高阶拓扑绝缘体-在声学\光学和电学等系统中相继被报道。高阶拓扑绝缘体所表现出的奇异拓扑性质激发了人们极大的研究热情。但是，磁学系统中是否存在高阶拓扑相还是一个有待解决的问题。

来自电子科技大学的严鹏教授领导的团队，报道了一种基于磁涡旋的呼吸型kagome晶格，可以实现高阶拓扑绝缘相（角态），通过调节两种晶格常数的比值，系统可以在普通绝缘相和高阶拓扑绝缘相之间转变。对三角形格子，角态存在于晶格的三个顶点，而对平行四边形格子，角态只存在于其中一个锐角顶点。观察到的角态振荡模式不受系统缺陷和无序的干扰，能保持很好的拓扑稳定性。微磁学全模拟验证了理论预言。该研究结果为磁性系统中实现高阶拓扑绝缘体开辟了道路，并将激励实验专家们在当前技术条件下对这种新奇拓扑态进行观测。

该文近期发表于npj Computational Materials 5: 107 (2019)，英文标题与摘要如下，点击左下角“阅读原文”可以自由获取论文PDF。

Higher-order topological solitonic insulators 

Zhixiong Li, Yunshan Cao, Peng Yan & Xiangrong Wang 

Pursuing topological phase and matter in a variety of systems is one central issue in current physical sciences and engineering. Motivated by the recent experimental observation of corner states in acoustic and photonic structures, we theoretically study the dipolar-coupled gyration motion of magnetic solitons on the two-dimensional breathing kagome lattice. We calculate the phase diagram and predict both the Tamm-Shockley edge modes and the second-order corner states when the ratio between alternate lattice constants is greater than a critical value. We show that the emerging corner states are topologically robust against both structure defects and moderate disorders. Micromagnetic simulations are implemented to verify the theoretical predictions with an excellent agreement. Our results pave the way for investigating higher-order topological insulators based on magnetic solitons.