学　术

　　由电子科学与工程学院主办的“电子论坛”第77期邀请到澳大利亚Wollongong大学Prof. Chao Zhang，与我校师生共同探讨拓扑材料电磁特性。具体安排如下，欢迎感兴趣的师生参加。

　　主　题：Charge dynamics and magneto-optics of topological materials

　　时　间：2019年6月11日（周二）10:00-11:30

　　地　点：沙河校区　逸夫楼521室

　　主讲人：Prof. Chao Zhang （Professor of Physics and Director of Quantum Devices, Optics and Solids, University of Wollongong）

　　内容简介：

　　We discuss some thermionic, optical and transport properties of three dimensional Dirac materials. (1) In 3D Dirac materials, the energy equipartition theorem gives rise to an average energy of kBT. This is twice of the energy in traditional materials. This enhanced energy leads to an enhanced thermionic cooling efficiency which is higher than that in normal metal and in graphene. (2) Fast charge dynamics has been studied, taking into account the electron-acoustic photon and electron-optical phonon interaction. Results indicate that the charge relaxation is directly proportional to the gap.  (3) Electronic structure of a Weyl semimetal and superconducting Weyl semimetal has been calculated. A dual gap structure has been revealed. The Andreev reflection can be used to directly map out the dual gap characteristics. (4) The shape of the Fermi surface of topological nodal-ring semimetals at low carrier concentrations is characterized by the ring radius b/hvF. This peculiar topological property may not have a clear signature in measurable physical quantities. We demonstrate an accurate and definitive method to determine the radius of topological nodal-ring semimetals. Under a magnetic field along the ring axis, the axial magneto-optical response has a giant peak. The position of this ultra-strong response is at the frequency of exactly 2b and is independent of the strength of the magnetic field.

　　主讲人简介：

　　Professor Chao Zhang received his PhD in physics in 1987 from City University of New York, USA. From 1987 to 1989, he was a postdoctoral fellow at Max-Planck-Institute for Solid Research in Stuttgart, Germany, working on quantum magneto-transport in semiconductor nanostructures. From 1989 to 1992, He was a research associate at Canada’s Meson Research Facility in Vancouver, working on quantum coherence and dissipation in solids. Since 1993, he has been a tenured faculty member in the School of Physics, University of Wollongong, Australia. Currently he is a senior professor of physics. From 2004-2014, he served as the associate director of the Institute of Superconducting and Electronic Materials. He is a Fellow of Australian Institute of Physics. He is the associate editor of Frontier of Optolelectronics and a member of the editorial board of Scientific Reports. He is an advisory member of the International Organizing Committee for Infrared, Millimeter and Terahertz Waves. His research interest is in the areas of quantum transport of nanostructures, terahertz photonics, nonlinear dynamics of semiconductors, graphene and topological insulators. He has published more than 250 papers including Nature Communications, Science Advances, Physical Review Letters, Physical Review, Applied Physics Letter, and Advanced Materials. He has received several awards including, JSPS Fellow 2001, Norwegian Research Council Senior Fellow 1996, Australian Academy of Sciences International Award 1999, 2000, 2004.

　　　　　　　　　　　　　　　　　　　　　　 电子科学与工程学院

　　　　　　　　　　　　　　　　　　　　　　　　2019年6月6日