Two-dimensional (2D) magnets decouple from the substrates, allow electrical control, and are mechanically flexible, making them integratable into emergent heterostructures for advanced properties and applications previously impossible. Among them, antiferromagnets hold promise for high-speed, low-power spintronics because they have magnetic resonance frequencies in the terahertz regime, null stray field for vanishing cross-talk between adjacent bits, and robustness against the external magnetic field perturbation. However, there is no good way to probe the magnetic states of the antiferromagnets in the 2D limit, due to their atomic thickness and net vanishing magnetization. In this talk, by means of electrical transport and optical spectroscopy measurements under low temperature and high magnetic field, I will give a few examples to study the magnetic evolution processes of 2D antiferromagnetic materials down to monolayer limit. For example, we detected the subtle phase transition behavior of exfoliated stripy antiferromagnet CrOCl under varying temperature and magnetic field and clarified its controversial spin structure, multiple degrees of freedom coupling of CrOCl under the 2D limit, and unraveled the odd-even layer-number effect and layer-dependent magnetic phase diagrams in A-type anitferromagnet MnBi2Te4.
Yu Ye is an assistant professor in the School of Physics at Peking University. He received his Ph.D. degree in condensed matter physics from Peking University in 2012. Prior to joining PKU in July 2016, Yu was working as a postdoctoral researcher at the University of California, Berkeley. His group (http://faculty.pku.edu.cn/yeyu) currently is interested in light-matter interactions and electrical transport properties in condensed matter physics, with an emphasis on novel physical phenomena emerging in atomically-thin materials, van der Waals heterostructures and surfaces/interfaces by nanoscale device designs, low-T-high-B optical spectroscopy, and electrical transport measurements. Yu published more than 90 research papers and earned >6200 citations with an h-index of 36.