报告题目：Probing and tuning quantum transport in topological phases of matter

报告人：刘金雨，Department of Physics and Astronomy, University of California, Irvine

时间：2023年12月15日(周五）10：00

地点：物理系B315

Abstract: The exploration of novel quantum materials advances our fundamental understanding of matter and unlocks the potential for technological breakthroughs, from energy harvesting to quantum sensing and computing. Over the past two decades, topological materials representing new quantum phases of matter have generated enormous interest in condensed matter physics research. In their electronic band structure, these materials are characterized by nonzero topological invariants, a concept derived from geometry. This unique characteristic enables them to host unprecedented functional properties, such as dissipationless edge conduction, that are robust against the presence of local defects.

In this talk, I will first introduce our transport study in a group of layered topological semimetals, including probing the interlayer tunneling of Weyl fermions in the 0th Landau levels and detecting the 3D quantum Hall effect and chiral surface transport of 2D confined Dirac fermions. Second, I will discuss our recent work on tuning the topological transport by applying strain. In this study, we successfully tuned the topological states in HfTe5 by applying strain and probed the distinct electronic and magnetic field responses across the topological phase transition from a weak to a strong topological insulator.

Finally, we pursue the finest synthesis of high-quality single crystals of quantum materials and develop a cold transfer method to fabricate pristine low-dimensional devices for air-sensitive van der Waals materials. We uncovered anomalous Hall signals led by the striking Berry curvature distribution and found unexpected superconductivity in HfTe5 nano flakes. These results reflect state-of-the-art experimental approaches to probe and control the electronic transport properties of topological quantum materials, holding high promise in creating novel quantum devices.

Bio: Dr. Jinyu Liu is a postdoctoral researcher working in the Quantum Materials and Device Lab at the University of California, Irvine. His passion lies in discovering new quantum materials and investigating their exceptional quantum properties with the aim of fabricating more resilient quantum devices. Throughout his PhD studies at Tulane and previous postdoctoral experience at UCLA, he has honed his expertise in growing high-quality single crystals of novel quantum materials, including topological materials, van der Waals materials, etc. He continuously seeks out novel techniques to probe and fine-tune the underlying states of these materials. His research achievements have been recognized and featured by multiple U.S. national labs and funding organizations. Dr. Liu takes great pleasure in collaborating with colleagues around the world in the exploration of remarkable quantum states of matter.

刘金雨博士从事新型量子材料的单晶合成以及其物性测量与调控的研究工作。已发表的论文中，在拓扑体材料和一维单晶纳米线的物性探索等方面作出了以下创造性的工作：1）发现了层状拓扑材料AMnSb2中不同类型的反磁性和狄拉克费米子及其相互作用；2）深入探索了AMnX₂中奇异的输运性质，包括零级外尔费米子的量子遂穿效应以及3D量子霍尔效应；3）合作引领了通过力学剥离方法获得Ta₂Pd₃Se₈类材料的一维晶体纳米线的研究；4）通过施加应力的方式实现HfTe₅的拓扑相变，并探测其表面态的输运性质。已累计在国际主流期刊发表论文40余篇，其中一作(含共一)论文10余篇，根据谷歌学术档案，总被引用2000余次。其研究成果多次被国内外线上科普媒体报道，并引起同行们的广泛关注和后续跟进研究。未来，刘博士希望继续新型量子材料的生长探索, 利用新型实验方法进行体材料的合成和器件制作，并采用不同实验手段进行量子材料的物性调控，以求在物理意义上探本溯源，进而力求在实际应用上有所突破。