Zhenyu Zhang, University of Science and Technology of China & Harvard University
Abstract
Much of our current research is centered on devising various ingenius approaches to squeeze the conduction electrons of matter into lower dimensions for their emergent exotic properties and potential technological applications. In this talk, I will start with a brief overview on how the quantized motion of conduction electrons within an ultrathin yet conventional metal film on a foreign substrate could lead to quantum stability of the film, signified by the existence of magic film thicknesses for growing atomically smooth films and a rich variety of functional properties of such quantum films. I will then move from systems of such simple or more conventional metals, to a new class of quantum materials termed topological insulators (TI), which are insulating in bulk form but possess topologically protected metallic surface states (TSS). Here our emphasis will be on how to gain precise tunability of the vertical location of such TSS using a conventional insulator (CI) as an ultrathin overlayer on top of a TI substrate. We reveal rich topological phase transitions in such CI/TI systems induced by dual-proximity effects, and speculate on the potential technological significance of these intriguing properties. Throughout the talk, the predictive power of first-principles based modeling and simulations will be highlighted.
Speaker Biography: Professor Zhenyu Zhang, a condensed matter theorist, received his Ph.D. in physics at Rutgers University in 1989. Until the end of 2010, he was a Distinguished Research Scientist in the Materials Science & Technology Division of Oak Ridge National Laboratory and Professor of Physics at the University of Tennessee, USA. At the beginning of 2011, he shifted his primary job base to USTC as a Qian-Ren Professor and serves as co-founding director of the International Center for Quantum Design of Functional Materials (ICQD) based at USTC. He is also an adjunct professor of physics at the University of Texas at Austin. He has authored 185 peer-reviewed papers, and many of those papers were in close collaboration with experimentalists. One of his most recent research emphases has been on predictive modeling of functional materials for solar energy conversion and storage. He is a fellow of the American Physical Society, and currently serves on the editorial boards of several professional journals (including Physical Review Letters).