ABSTRACT
Flows need sources and sinks. That is why, in a new class of exotic materials called Weyl semimetals, the sources and sinks of Berry curvature—doubling Weyl points—were believed to exist only in pairs constrained by Nielson-Ninomiya no-go theorem. Very recently, we have observed unpaired Weyl points for the first time in a crystalline solid PtGa [1]. There exist a 2D Weyl nodal wall in PtGa which circumvents the no-go theorem [2]. This discovery, which upends conventional thinking about Nielson-Ninomiya no-go theorem, demonstrates the unique properties of “nodal wall” Weyl semimetals in comparison to conventional Weyl systems having only zero-dimensional Weyl nodes.
References
[1] Ma, JZ., Wu, QS., Song, M. et al. Observation of a singular Weyl point surrounded by charged nodal walls in PtGa, Nat. Commun. 12, 3994 (2021).
[2] Yu, Z.-M., Wu, W.-K., Zhao, Y. X., and Yang, S. A. Circumventing the no-go theorem: A single Weyl point without surface Fermi arcs. Phys. Rev. B 100, 041118 (R) (2019).
BIOGRAPHY
Dr. Junzhang Ma joined the department of physics, City University of Hong Kong as an assistant professor in the January of 2021. He got the degree of Doctor of Philosophy in 2017 from Institute of Physics (IOP), Chinese Academy of Science in Prof. Hong Ding’s group. He furthered his research career as a joint postdoctoral fellow in Swiss Light Source, Paul Scherrer Institute (PSI) and École Polytechnique Fédérale de Lausanne (EPFL) in Switzerland supported by Prof. Ming Shi (Senior Scientist, PSI Director Assistant) and Prof. Joël Mesot (the current President of ETH). Dr. Ma’s research mainly focuses on electronic structure of topological materials, superconductivity, low-dimensional materials, and correlated materials, studied by Angle Resolved Photoemission Spectroscopy (ARPES). He has more than 30 publications in high-impact journals such as Nature, Nature Physics, Science Advance, Nature Communications, Physical Review X, Physics Review Letters, Advanced Materials, Nano Letters, etc. These works include many breakthrough results such as the discoveries of Weyl semimetal, three-component Fermion, Hourglass Fermion, fluctuated magnetic Weyl semimetal, etc.
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