Acoustic spin-1 Weyl semimetal
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gust 2020 Vol. 63 No. 8: 287032 https://doi.org/10.1007/s11433-020-1558-8
Acoustic spin-1 Weyl semimetal 1†
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WeiYin Deng , XueQin Huang , JiuYang Lu , Feng Li , JiaHong Ma , 3* 2,4* ShuQi Chen , and ZhengYou Liu 1
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School of Physics and Optoelectronics, South China University of Technology, Guangzhou 510640, China; Key Laboratory of Artificial Micro- and Nanostructures of Ministry of Education, School of Physics and Technology, 3
Wuhan University, Wuhan 430072, China; Key Laboratory of Weak Light Nonlinear Photonics of Ministry of Education, School of Physics, Nankai University, Tianjin 300071, China; 4 Institute for Advanced Studies, Wuhan University, Wuhan 430072, China Received February 8, 2020; accepted April 3, 2020; published online June 16, 2020
The study of topological semimetals hosting spin-1 Weyl points (WPs) beyond Dirac points and WPs has attracted a great deal of attention. However, a spin-1 Weyl semimetal that exclusively possesses spin-1 WPs in a clean frequency window without being shadowed by any other nodal points is yet to be discovered. This study reports a spin-1 Weyl semimetal in a phononic crystal. Its spin-1 WPs are touched by two linear dispersions and an additional flat band and carry monopole charges (−2,0,2) or (2,0,−2) for the three bands from the bottom to the top. They result in double Fermi arcs, which occur between the first and second bands, as well as between the second and third bands. Further robust propagation is observed against the multiple joints and topological negative refraction of the acoustic surface arc wave. The results of this study create the basis for the exploration of the unusual properties of spin-1 Weyl physics on a macroscopic scale. spin-1 Weyl point, phononic crystal, topological surface states PACS number(s): 43.40.+s, 63.20.–e, 03.65.Vf Citation:
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W. Y. Deng, X. Q. Huang, J. Y. Lu, F. Li, J. H. Ma, S. Q. Chen, and Z. Y. Liu, Acoustic spin-1 Weyl semimetal, Sci. China-Phys. Mech. Astron. 63, 287032 (2020), https://doi.org/10.1007/s11433-020-1558-8
Introduction
The discovery of Dirac and Weyl semimetals [1-8] featuring fourfold and twofold linear crossing points in their band structures has opened up a new field of research known as topological semimetals [9,10]. The low-energy excitations near the Dirac points and Weyl points (WPs) are described by the Dirac and Weyl equations; thus, they behave like Dirac and Weyl fermions, i.e., the relativistic spin-1/2 fermions in *Corresponding authors (Feng Li, email: [email protected]; ShuQi Chen, email: [email protected]; ZhengYou Liu, email: [email protected]) †These authors contributed equally to this work.
quantum field theory. Unlike the fermions in high-energy theories, the excitations in crystals are protected by the rich symmetries of the space group (rather than the Poincaré symmetry) and give rise to new physical phenomena, such as type-II Weyl semimetals [11], nodal line semimetals [12], and spin-1 Weyl semimetals [13]. The spin-1 Weyl semimetals, which exclusively host spin-1
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