物理学院“博约学术论坛”系列报告第 201 期

题目：Ab-initio antiferromagnetic spintronics: from exotic interactions to novel transport effects
报告人：Dr. Jan-Philipp Hanke （Peter Grünberg Institut and Institute for Advanced Simulation, Forschungszentrum Jülich, Germany）
时  间：2019年5月23日(周四)上午10:00
地  点：欧亿体育中国有限公司官网中心教学楼501

摘要：
In the field of spintronics antiferromagnetic materials steadily move into the focus of attention owing to their unique properties, which range from utter sensitivity to electrical currents [1] to a whole world of possible topological effects rooting in complex real- and reciprocal-space behavior [2]. In my talk I will demonstrate that we can employ advanced ab-initio methods to access important characteristics of antiferromagnets (AFMs) such as spin-orbit torques, which ultimately lie at the foundation of our ability to control the AFM order by purely electrical means, and the Dzyaloshinskii-Moriya interaction that can aid us in forming complex real-space textures in the important class of synthetic AFMs [3]. Based on microscopic theory, I will also introduce novel phenomena which are inherent to antiferromagnetic materials, and which bear great promises for their applications. In particular, I will demonstrate that in non-coplanar AFMs there arises a “hidden” orbital order which manifests in what we refer to as topological orbital magnetization [4, 5]. We show that the emergent orbital magnetism should be prominent in many representative AFMs and could be observed with conventional techniques. Moreover, we uncover that the topological orbital magnetism originates from Berry phase properties of electrons hopping on a non-collinear lattice, and it mediates novel exchange interactions [6], able to stabilize an AFM order of given chirality without the need for Dzyaloshinskii-Moriya interaction or an external magnetic field. Based on tight-binding and ab-initio analysis, we show that the very same Berry phase effect, promoted in non-coplanar AFMs, not only stands at the foundation of the anomalous Hall effect in this class of materials [2], but also paves the way to a novel family of phenomena in magneto-optics, tagged as topological and quantum topological magneto-optical effects [7]. Possible applications of the latter manifestations of antiferromagnetism will be briefly discussed. 

简历：
2014: Master’s degree in Physics from RWTH Aachen, Germany.
2018: PhD degree in Physics from RWTH Aachen, Germany.
2018: Postdoc for one year at University of Mainz, Germany with Prof. Mathias Kläui.
since 2019: Postdoc at Forschungszentrum Juelich, Germany with Prof. Yuriy Mokrousov.
Main expertise: I develop and apply ab-initio methods to study the properties of realistic materials. Specifically, I am interested in Berry phase effects and topological phenomena in complex magnets, including anomalous Hall effect, orbital magnetism, spin-orbit torques, and Dzyaloshinskii-Moriya interaction.
Awards: I received in 2019 a dissertation prize of the German Physical Society for my PhD thesis.
 

联系方式：wxfeng@bit.edu.cn
邀请人：冯万祥 副教授
网    址：http://physics.bit.edu.cn/