Optical Response of Layered Topological Semimetals
Two dimensional (2D) materials and topological materials are two important areas attracting enormous research interest in condensed matter physics and materials sciences. Although the overlap of these two fields dated back to layered topological insulator eg. Bi2Se3 et al, it's not until recent experimental verification of type-II Dirac/Weyl semimetal and quantum spin hall insulator in 2D layered transitional metal dichalcogenides (TMD) family that these two fields have merged together unprecedently. The emergence of 2D layered topological materials bring the novel topological properties to 2D materials family, as 2D layered materials can be conveniently integrated into van der Waals heterostructures by stacking multiple 2D layered species. In this talk, I will introduce our group's recent progress on the optical response of 2D layered topological semimetals. We will start to introduce our early effort on exploring the potential of these materials for photo detection with photoexcited carrier dynamics  and scanning photocurrent studies , then we will discuss the experimental possibilities to probe the exotic optical response that is related to the chirality of carriers and divergence of Berry curvature at the nodel points of these materials with mid-IR probe .
 Advanced Materials 28, 4845 (2016); Physics Review B 95, 024303 (2017); arXiv:1807.03049 (2018)
 Nano Letters 17, 834 (2017); Advanced Materials 30, 1707152 (2018); ACS Nano 12,4055 (2018)
 arXiv: 1806.08508 (2018)
Dong Sun, associate professor in International Center of Quantum Materials of Peking University, China. He obtained his bachelor degree in physics from University of Science and Technology of China in 2004 and Ph.D in physics from University of Michigan in 2009 with Professor Theodore Norris. After that he works as postdoc research fellow in Center for Ultrafast Optics Science of University of Michigan and research scientist in University of Washington. In 2012, he was recruited by the youth thousand talent program of China and started to work in international center for quantum materials of Peking University and got tenured in 2017. His research mainly focusing on using various ultrafast spectroscopy method, including pump probe spectroscopy, scanning photocurrent spectroscopy and THz spectroscopy to study various quantum materials and functional optoelectronics devices.