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When spintronics meets topology: symmetry-protected zero modes in spin-texture based metamaterials (Part I) and twisted magnon as a magnetic tweezer (Part II)

创建于2019年12月30日 星期一作者 : 科研办 浏览量 :

主讲人:严鹏,电子科技大学教授

  间:20201310:00

  点:物电澳门新普京下载A219

联系人:李福祥

讲座摘要:In the first part of my talk, we show the emergence of second-order topological insulator in the dynamics of spin texture based metamaterials. Quantized Chern number and ZN 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.

 

Wave fields with spiral phase dislocations carrying orbital angular momentum (OAM) have been realized in many branches of physics, such as for photons, sound waves, electron beams, and neutrons. However, the OAM states of magnons (spin waves), the building block of modern magnetism, and particularly their implications have yet to be addressed. In the second part of my talk, we theoretically investigate the twisted spin-wave generation and propagation in magnetic nanocylinders. The 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.

 

 

主讲人简介:严鹏,电子科技大学教授,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。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,2016年入选中组部青年千人计划。团队目前拥有国家特聘教授2人,副教授1人,博士后4人。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,取得了一系列国际领先,创新性的成果,澄清了磁学和自旋电子学领域一些长期存在的基本问题,预言了磁振子传递自旋转移力矩的新机制,在国际上产生了广泛的影响,在Physical Review Letters, Physical Review B (E, Applied)等期刊发表高水平论文30余篇,部分理论预言已经得到国际一流研究组的实验证实。长期担任Physics Reports, Physical Review Letters, Physical Review X, Science Advances等期刊审稿人。回国独立开展工作三年多来,已带领团队成功申请到国家自然科学基金5项,获批中国博士后科学基金面上和特别资助5项,发表多篇高水平研究论文,2018-2019年以通讯作者身份指导团队研究生和博士后在国际著名期刊Physical Review Letters, npj Computational Materials, Physical Review Applied, Physical Review B, Physical Review E, Optics Express发表论文14(电子科技大学均为唯一或第一完成单位)

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