Quantum materials are believed to be key for many next-generation technologies, such as sensing, computing, modeling or communication, with higher accuracy or efficiency. Particularly, the magnetic quantum materials are promising for spintronic applications due to the interplay of magnetic order with electronic properties. To study the intrinsic material properties and evaluate the performance of novel devices fabricated from these materials, a high material quality is necessary. Otherwise the desired properties might be obscured. In my presentation, I will talk about two distinct magnetic quantum material systems, and particularly their extraordinary electronic, magnetic, and structural properties, which are enabled by high crystal quality. The first part of my talk will focus on magnetic van der Waals (vdW) materials. Despite the rapid advances in recent years, so far magnetic vdW materials are mainly insulating or semiconducting, and none of them possesses a high electronic mobility. The realization of high mobility in a magnetic vdW material, however, has been long sought and is recently recognized to be critical for the design of novel magnetic twistronic devices. Here I will introduce an antiferromagentic vdW material with a record-high electronic mobility, which is comparable to that of black phosphorus, and is only surpassed by graphite. Furthermore, I show that this material can be mechanically exfoliated down to monolayers. The combined properties of antiferromagnetism, high mobility and easy exfoliation establish it as a distinct member in the growing pool of 2D materials. In the second part of my talk, I am going to introduce a novel magnetic topological semimetal. I will show how stoichiometry control affects the crystal structure and introduces charge density waves, which couples with the electronic structure and leads to the formation of novel topological phases.
Dr. Shiming Lei is currently a postdoc with Prof. Leslie Schoop in the Chemistry department at Princeton University. He obtained his PhD degree in the Department of Materials Science and Engineering at the Pennsylvania State University in December, 2017. His PhD research mainly focused on materials with no inversion symmetry, including ferroelectric materials, multiferroic materials and magnetic polar metals. With a combination of various experimental tools, including transmission electron microscopy, scanning probe microscopy, and nonlinear optical spectroscopy and imaging, his research theme was to understand materials’ multi-scale microstructure-property relationship, and particularly the rich coupling phenomena under various external stimuli, such as electric field, magnetic field, and uni-axial tensile stress. As a postdoc at Princeton University, his interests expanded to topological materials and 2D van der Waals crystals. His current work focuses on the development of novel materials, high-quality crystal growth, and material properties that highlight symmetry, topology, magnetism, and their couplings. Dr. Lei frequently serves as a reviewer for various journals, such as Physical Review X, Physical Review Letters, Physical Review B, Physical Review Materials, Physical Review Research, Nature Communications, Advanced Materials, Inorganic Chemistry, etc. He is currently a member of APS.