Abstract：

　　Realization of long-range magnetic order in two-dimensional (2D) van der Waals magnets facilitates exploitation of exotic emergent magnetic properties in reduced dimensionality. Here we report our recent progresses surrounding rich topological properties of 2D magnets via element mutation. Starting with the parental 2D ferromagnet CrI₃, we first show that proper mutation of Cr with neighboring transition metal elements lead to new stable 2D ferromagnets CrMnI6 and CrVI₆, which exhibit nontrivial band topology upon optimal band-filling. Next we reveal giant Dzyaloshinskii-Moriya (DM) interactions in these magnets, which stem from the in-plane inversion symmetry breaking and can give rise to intriguing topological excitations. In particular, for monolayered CrMnI₆, we predict the existence of strong anisotropic biquadratic exchange in addition to the giant DM interaction, which in turn give rise to bimeronic excitations that exhibit magnon-driven ratchet dynamics. For the newly predicted and synthesized CrVI₆, we reveal striking bump features in the hysteresis loop of the Kerr rotation angles, and the resultant topological Kerr effect (TKE) can be exploited as a magneto-optical fingerprint of skyrmionic excitations detected in a non-invasive manner.

报告人简介：

　　张顺洪博士，中国科学技术大学国际功能材料量子设计中心特任研究员，2016年获得北京大学工学院博士学位，2016-2018年在清华大学高等研究院开展博士后研究工作（获得首批“博新计划”资助），2018年加入中国科学技术大学，主要从事低维材料、拓扑电子材料及量子磁性材料的模拟研究，曾在PNAS、JACS、Adv. Funct. Mater.、Nano Lett.、PRB/Mater/Research等学术期刊发表论文40余篇。近期主要开展量子磁性材料中复杂磁相互作用及低能拓扑磁激发等物性研究。