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Magnonic Topological States and Spinwave Devices

来源:合肥微尺度物质科学国家实验室    浏览次数:0


报告题目   Magnonic Topological States and Spinwave Devices
报告人   王向荣 教授
报告人单位   香港科技大学
报告时间   2018-07-09   10:00
报告地点   合肥微尺度物质科学国家研究中心九楼会议室(9004)
主办单位   合肥微尺度物质科学国家研究中心、国际化学理论中心(ICCT)
报告介绍
Abstract:
Topological matters have attracted lots of attention in recent years because of their interesting and exotic properties. One such property is the existence of unidirectional and topologically protected surface/edge states that are robust against internal and external perturbations. The study was initially exclusive for electron systems and was believed to be a quantum phenomenon. It is now known that the topological states can exist in classical mechanics and photonics. Topological states can also exist in magnetic materials govern both by quantum mechanics at the zero temperature and by classical magnetization dynamics at finite temperatures.
Magnetic materials are highly correlated spin systems that do not respect the time-reversal symmetry. The low-energy excitations of magnetic materials are spin waves whose quanta are magnons. In the ambient temperature, the magnetization dynamics of real magnetic material shall be govern by the Landau- Landau-Lifshitz-Gilbert (LLG) equation. Like electronic materials that can be topologically nontrivial, magnetic materials govern by the LLG equation can also be topologically nontrivial with topologically protected edge spin waves. Unlike the normal spin waves that are very sensitive to the system changes and geometry, these edge spin waves are robust against internal and external perturbations such as geometry changes and spin wave frequency change. Therefore, the magnetic topological matter is of fundamental interest and technologically useful in magnonics. We will see several examples of magnonic topological materials, including pyrochlore [1] and stacked honeycomb [2] ferromagnets as Weyl magnons, as well as perpendicularly magnetized two-dimensional films with Dzyaloshinskii-Moriya and/or pseudodipolar interactions as generic magnonic insulators [3,4]. The edge spin waves in these magnonic materials are robust against perturbations. An interesting functional magnonic device called beamsplitter and interferometer can be made out of a domain wall in a strip. It is shown that an in-coming spin wave beam along one edge splits into two spin wave beams propagating along two opposite directions on the other edge after passing through a domain wall.
 
报告人简介:
王向荣,香港科技大学终身教授;1984年毕业于武汉大学物理系;1990年在美国罗彻斯特大学(University of Rochester)获博士学位;是山东大学、武汉大学等多所学校和研究机构的客座教。研究方向:在凝聚态理论领域具有丰富研究经验,研究领域包括量子霍尔效应,二维电子气量子输运,超晶格以及磁动力学中;迄今已在国际权威学术杂志发表论文过百篇。

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