Speaker: Shun-Qing Shen (Dep. of Physics, University of Hong Kong)
Chiral anomaly is a purely quantum mechanical phenomenon of massless Weyl fermions in quantum field theory. Its manifestation in condensed matter has been extensively studied theoretically and experimentally. The negative magnetoresistance in which a resistance decreases with increasing external applied magnetic field B with non-zero E·B is widely regarded as a signature of chiral anomaly in Weyl/Dirac semimetals, however, it encounters some challenges as the negative magnetoresistance can also be produced by other mechanisms in topological materials and semiconductors with strong spin-orbit coupling. Here I shall introduce both theory of quantum magnetotransport of Weyl fermions and the experimental observation in the Dirac semimetal Cd3As2 of negative magnetoresistance, giant anisotropic magnetoresistance and planar Hall effect. The chiral anomaly of Weyl fermions can account for the high anisotropy and the minus sign in this isotropic and paramagnetic material. In addition to the negative magnetoresistance, this observation provides one more evidence to confirm the chiral anomaly in topological semimetals in a different perspective.
Biography of Prof. Shun-Qing Shen
Professor Shun-Qing Shen, an expert in the field of condensed matter physics, is distinguished for his research works on topological insulator, quantum transport theory, spintronics of semiconductors, quantum magnetism and orbital physics in transition metal oxides, and novel quantum states of condensed matters, and strong correlated electron systems. He has published a single-authored monograph, Topological Insulators (Springer, 1st ed., 2012; 2nd ed., 2017), which is the first book on the topic. He was awarded Croucher Senior Research Fellowship (The Croucher Award) in 2010, and “Outstanding Researcher Award” in the University of Hong Kong in 2013.
Professor Shen has been a professor of physics at The University of Hong Kong since July 2007. Professor Shen received his BS, MS, and PhD in theoretical physics from Fudan University in Shanghai. He was a postdoctorial fellow (1992 – 1995) in China Center of Advanced Science and Technology (CCAST), Beijing, Alexander von Humboldt fellow (1995 – 1997) in Max Planck Institute for Physics of Complex Systems, Dresden, Germany, and JSPS research fellow (1997) in Tokyo Institute of Technology, Japan. In December 1997 he joined Department of Physics, The University of Hong Kong.
Time: 16:00pm, Nov. 30, 2017
Location: Rm. S306, UCAS Zhong-Guan-Cun Teaching Building [map]