Junwei Liu Seminar
12:30 pm - 1:15 pm, plus Q & A
SERC Building, room 703
Title: Topological Phases in Transition Metal Chalcogenides
Speaker: Junwei Liu, Hong Kong University of Science and Technology, Dept of Physics
For individuals who will not be on Temple's campus, Dr. Liu' lecture can be accessed through WebEx. The meeting number is: 646 010 832
The discovery of quantum spin Hall effect engendered a new chapter of topological materials research in condensed matter physics and materials science. In this talk, I will introduce some of our recent theoretical works about the topological phases in 2D and 3D transition metal chalcogenides. We predict monolayer MX2 (M=Mo, W; X=S, Se, Te) of 1T’ structure could realize quantum spin Hall insulator. Moreover, their topology can be easily tuned by external electric field, which motivated us to propose a new type of transistor, called topological field transistor. More recently, we found another new class of transition metal chalcogenides MM’Te4 (M=Nb, Ta; M’=Ir, Rh) could be quantum spin Hall insulators in 2D and Weyl semimetals in 3D. I will also discuss some recent transport, ARPES and STM experiments on monolayer WTe2, where many of the observations are consistent with monolayer WTe2 being a 2D TI.
 X. Qian, J. Liu, L. Fu, J. Li，Science 346, 1344 (2014)
 J. Liu, H. Wang, C. Fang, L. Fu, X. Qian, Nano Lett. 17 467-475 (2017)
Junwei Liu has a broad interest in condensed matter physics, from the traditional phenomena like ferroelectricity to the exotic topological phases like quantum spin Hall insulators. Currently, his research mainly focuses on two parts: 1) the novel topological phases of matter, especially the symmetry-related topological phases, and their material realizations and experimental signatures; 2) applications of advanced machine learning techniques in physics, especially the combination of machine learning techniques and quantum Monte Carlo simulations.