PT  - JOURNAL ARTICLE
AU  - Yuan, Qian-Qian
AU  - Zhou, Liqin
AU  - Rao, Zhi-Cheng
AU  - Tian, Shangjie
AU  - Zhao, Wei-Min
AU  - Xue, Cheng-Long
AU  - Liu, Yixuan
AU  - Zhang, Tiantian
AU  - Tang, Cen-Yao
AU  - Shi, Zhi-Qiang
AU  - Jia, Zhen-Yu
AU  - Weng, Hongming
AU  - Ding, Hong
AU  - Sun, Yu-Jie
AU  - Lei, Hechang
AU  - Li, Shao-Chun
TI  - Quasiparticle interference evidence of the topological Fermi arc states in chiral fermionic semimetal CoSi
AID  - 10.1126/sciadv.aaw9485
DP  - 2019 Dec 01
TA  - Science Advances
PG  - eaaw9485
VI  - 5
IP  - 12
4099  - http://advances.sciencemag.org/content/5/12/eaaw9485.short
4100  - http://advances.sciencemag.org/content/5/12/eaaw9485.full
SO  - Sci Adv2019 Dec 01; 5
AB  - 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 p-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.