报告人：严鹏 教授，电子科技大学电子科学与工程学院

报告时间：2019年12月23日（周一）下午3:00

报告地点：知新楼C座1113报告厅

邀请人：解士杰 教授，高琨 副教授

报告摘要：

(Part I) We show the emergence of second-order topological insulator in the dynamics of spin texture based metamaterials. Quantized Chern number and Z_N Berry phase are proposed to completely characterize the nontrivial topology. By studying the collective gyration of magnetic vortices in a breathing honeycomb lattice, we derive the full phase diagram and show that the topological “zero-energy” corner mode is protected by a generalized chiral symmetry in the sexpartite lattice, leading to particular robustness against disorder and defects. Interestingly, we observe corner states at either obtuse-angled or acute-angled corners, depending on whether the lattice boundary has an armchair or zigzag shape. Full micromagnetic simulations confirm the theoretical predictions with good agreement. This finding opens up a promising route for realizing higher-order symmetry-protected corner states in magnetic systems and for finally achieving topological spintronic memory, imaging, and computing. (Part II) We theoretically investigate the twisted spin-wave generation and propagation in magnetic nanocylinders. The orbital angular momentum (OAM) nature of magnons is uncovered by showing that the spin-wave eigenmode is also the eigenstate of the OAM operator in the confined geometry. Inspired by optical tweezers, we predict an exotic “magnetic tweezer” effect by showing skyrmion gyrations under twisted magnons in exchange coupled nanocylinder|nanodisk heterostructure, as a practical demonstration of magnonic OAM to manipulate topological spin defects. Our study paves the way for the emerging magnetic manipulations by harnessing the OAM degree of freedom of magnons.

报告人简介：

严鹏，教授，博导，2006年本科毕业于中国科技大学近代物理系，2011年于香港科技大学获得物理学博士学位，email: yan@uestc.edu.cn。

2011-2015年期间，先后在荷兰代尔夫特理工大学，日本东北大学，德国美因茨大学从事博士后研究工作，2015年底回国组建电子科技大学自旋电子学理论研究团队。主要研究方向为自旋电子学理论，拓扑磁动力学，自旋波动力学中的非线性效应，非平衡热力学与统计，生物磁性与磁导航。在Physical Review Letters, Physical Review B (E, Applied)等期刊发表高水平论文30余篇。

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