报告题目：Giant piezomagnetism and noncollinear spin current from C-paired spin valley locking

报 告 人：刘军伟教授（香港科技大学物理系）

报告时间：2023年4月10日（周一）上午9:30

报告地点：物理科学与技术学院D-505

报告摘要：

In this talk, I will take our recently proposed new type of spin-valley locking (SVL), named C-paired SVL, in antiferromagnetic systems. It directly connects the spin/valley space with the real space, and hence enables both static and dynamical controls of spin and valley to realize a multifunctional antiferromagnetic material. The new emergent quantum degree of freedom in the C-paired SVL is comprised of spin-polarized valleys related by a crystal symmetry instead of the time-reversal symmetry. Thus, both spin and valley can be accessed by simply breaking the corresponding crystal symmetry. Typically, one can use a strain field to induce a large net valley polarization/magnetization and use a charge current to generate a large noncollinear spin current. We predict the realization of the C-paired SVL in monolayer V2Se2O, which indeed exhibits giant piezomagnetism and can generate a large transverse spin current. Based on symmetry analysis and first-principles calculations, we also found C-paired SVL can exist in the following experimentally verified AFM materials, NaOsO₃, LaMnO₃, LaCrO₃, TbFeO₃, MnTe, RuO₂, MnF₂, FeF₂, CoF₂, and NiF₂. Our findings provide new opportunities to integrate various controls of spin and valley with nonvolatile information storage in a single material, which is highly desirable for versatile fundamental research and device applications.

报告人简介：

Prof. Junwei Liu obtained his PhD in the department of physics, Tsinghua University, in 2014, and then he started his postdoctoral research in Massachusetts Institute of Technology. He joined Hong Kong University of Science and Technology in 2017 as an assistant professor. Prof. Liu has a very broad interest in condensed matter physics and quantum physics, varying from the traditional phenomena like ferroelectricity to the exotic topological phases like quantum spin Hall insulators. He has published more than 50 papers including 2 in Science, 1 in Nature, 1 in Nature Physics, 3 in Nature Materials, 6 in Nature Communications, 2 in Physical Review Letters, 1 in Optica, 2 in Nano letters, 1 in Physical Review Materials, 1 in Adv. Mater., 2 in Physical Review Applied and 21 in Physical Review B. He was awarded National Natural Science Foundation of China Excellent Young Scientist (Hong Kong and Macau) in 2020.

邀 请 人：余睿 教授