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arXiv · 2002.08647

Quasiparticle Interference Evidence of the Topological Fermi Arc States in Chiral Fermionic Semimetal CoSi

Qian-Qian Yuan·Liqin Zhou·Zhi-Cheng Rao·Shangjie Tian·Wei-Min Zhao·Cheng-Long Xue·Yixuan Liu·Tiantian Zhang·Cen-Yao Tang·Zhi-Qiang Shi·Zhen-Yu Jia·Hongming Weng·Hong Ding·Yu-Jie Sun·Hechang Lei·Shao-Chun Li
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Abstract

Chiral fermions in solid state feature "Fermi arc" states, connecting the surface projections of the bulk chiral nodes. The surface Fermi arc is a signature of nontrivial bulk topology. Unconventional chiral fermions with an extensive Fermi arc traversing the whole Brillouin zone have been theoretically proposed in CoSi. Here, we use scanning tunneling microscopy / spectroscopy to investigate quasiparticle interference at various terminations of a CoSi single crystal. The observed surface states exhibit chiral fermion-originated characteristics. These reside on (001) and (011) but not (111) surfaces with pi-rotation symmetry, spiral with energy, and disperse in a wide energy range from ~-200 to ~+400 mV. Owing to the high-energy and high-space resolution, a spin-orbit coupling-induced splitting of up to ~80 mV is identified. Our observations are corroborated by density functional theory and provide strong evidence that CoSi hosts the unconventional chiral fermions and the extensive Fermi arc states.

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Qian-Qian Yuan, Liqin Zhou, Zhi-Cheng Rao, Shangjie Tian, Wei-Min Zhao, Cheng-Long Xue, Yixuan Liu, Tiantian Zhang, Cen-Yao Tang, Zhi-Qiang Shi, Zhen-Yu Jia, Hongming Weng, Hong Ding, Yu-Jie Sun, Hechang Lei, Shao-Chun Li. 2020-02-20. Quasiparticle Interference Evidence of the Topological Fermi Arc States in Chiral Fermionic Semimetal CoSi. https://doi.org/10.1126/sciadv.aaw9485

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