福利院体检120秒五次

Quantum Anomalous Semimetals

来源:福利院体检120秒五次
报告题目   Quantum Anomalous Semimetals
报告人   Prof. Shun-Qing Shen
报告人单位   Department of Physics, The University of Hong Kong
报告时间   2022-02-23 14:00:00
报告地点   福利院体检120秒五次物质科研B楼B0902会议室
主办单位   福利院体检120秒五次、国际功能材料量子设计福利院体检120秒五次(ICQD)
报告介绍

Abstract:

  The topological states of matter and topological materials have been attracting extensive interests as one of the frontier topics in condensed matter physics and materials science since the discovery of quantum Hall effect in 1980s. So far all the topological phases such as quantum Hall effect, quantum spin Hall effect and topological insulators and superconductors are characterized by a nonzero integer or Z and Z2 topological invariant. None is a half-integer or fractional. Here we propose a novel type of semimetals which hosts a single cone of Wilson fermions instead of Dirac fermions. The Wilson fermions possess linear dispersion near the energy crossing point, but breaks the chiral or parity symmetry such that an unpaired Dirac cone can be realized on a lattice. They are not prohibited by the Nielsen-Ninomiya theorem and avoid the fermion doubling problem. We find that the system can be classified by the relative homotopy group, and the topological invariant is a half-integer. We term the unexpected and nontrivial quantum phase as “quantum anomalous semimetal”. The topological phase is a synergy of topology of band structure in solid and quantum anomaly in quantum field theory. The work opens the door towards exploring novel states of matter with fractional topological charge.


Biography:

  Professor Shun-Qing Shen, an expert in the field of condensed matter physics, is distinguished for his research works on topological insulator, quantum transport, spintronics of semiconductors, quantum magnetism and orbital physics in transition metal oxides, and novel quantum states of condensed matters. He proposed topological Anderson insulator, theory of weak-localization and anti-localization in topological insulators, resonant spin Hall effect and theory of phase separation in colossal magnetoresistive (CMR) materials. He proved existence of antiferromagnetic long-range order and off-diagonal long-range order in itinerant electron systems. He has published a single-authored monograph, Topological Insulators (Springer, 2012), which is the first book on the topic. He was awarded Croucher Senior Research Fellowship (The Croucher Award) in 2010, Hong Kong, and Outstanding Researcher Award 2012-2013, The University of Hong Kong.

  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.

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