报告人：杨洪新

报告题目：First-principles study of Dzyaloshinskii-Moriya interaction and topological magnetism in 2D magnets

报告摘要：The Dzyaloshinskii-Moriya interaction (DMI) has attracted significant interest because it plays a tremendous role for fast domain wall motion and allows the creation of topological quasi-particles, e.g. magnetic skyrmions, chiral domain walls, and bimerons, etc., which are very promising for ultra-dense/ultra-low energy consumption information storage and logic devices. Spin-orbit coupling and absence of inversion symmetry are the two ingredients for the existence of DMI. Most state-of-the-art experiments and devices of today use the interface between two crystals to break the inversion symmetry and create DMIs, such as DMI in heterostructures between ferromagnetic metals and heavy metals or heterostructures between ferromagnetic metals and graphene. In those heterostructures, it is known that intricate adjustment of the layer thicknesses, stacking sequences, or chemical composition, etc., are often necessary to control the strength and/or chirality of DMI [Nat. Mater. 16, 898 (2017); Sci. Rep. 8, 12356 (2018)]. More interestingly, how to induce DMI in 2D magnets actually can even scale down the spintronics devices using topological spin textures. Basically, one can use Janus magnets, or intrinsic p-4m2 symmetry protected 2D magnets, etc. At the same time, it is a long-desired expectation to realize topological magnetism and its electric control for applications in information storage and logic technologies. Here, we propose that both can be achieved in two-dimensional (2D) magnetoelectric multiferroics simultaneously. We demonstrate that the obtained significant DMI is switchable and can promote tunable sub-10 nm skyrmions in 2D multiferroics with perpendicular magnetic anisotropy such as in a CrN or Co(MoTe2)2 monolayer. Based on the electrical switchable DMI [5], we designed one single nanotrack with complete logic functionality, which can be programmed via voltage-switched DMI. By reconstructing DMI chirality barriers, we successfully realize the annihilation, fusion and pinning of skyrmions, and then the complete Boolean family including AND, OR, NOT, NAND, NOR, XOR, and XNOR are implemented in one single nanotrack. We believe that this work represents an important step towards the development of all-electric manipulation of skyrmion-based logic and memory, paving the way for future skyrmionic in-memory computing.

报告简介：杨洪新，中国科学院宁波材料技术与工程研究所研究员，量子功能材料团队负责人。获国家海外高层次引进人才计划支持，于17年加入宁波材料所。 杨洪新研究员一直致力于自旋电子学理论计算研究，主要研究磁随机存储器以及磁斯格明子应用中涉及到的基本物理学现象。在自旋电子学领域主要贡献有：（1）发展了基于第一原理的投影轨道特征谱分析垂直磁各向异性，原子层分辨和轨道杂化分辨计算分析垂直磁各向异性的方法，阐明了铁磁材料/金属氧化物界面的巨大垂直磁各向异性的物理机制，预言了在MgO基磁隧道结可以同时实现巨大TMR和PMA，并获实验验证，解决了STT-MRAM的一个关键问题。（2）发展了基于DFT计算界面Dzyaloshinskii-Moriya interaction (IDMI)的方法，从而在第一性原理层面阐明了铁磁金属/重金属界面DMI的物理机制；预言多种界面DMI材料并提出多种调控方法，被大量实验所验证，获得同行的认可，为基于手性磁畴及Skyrmion的磁存储应用提供重要理论指导。已发表论文70余篇。Nature等杂志审稿人。在APS March Meeting等学术会议作邀请报告30余次。主持多项国家及省部级项目。 https://hongxinyang.nimte.ac.cn/leader.html