Fermi arcs on Weyl semimetals exhibit many exotic quantum phenomena.Usually found on atomically flat surfaces with approximate translation symmetry,Fermi arcs are rooted in the peculiar topology of bulk Bloch bands of 3D crystals.The fundamental question of whether a 1D Fermi arc can be probed remains unanswered.Such an answer could significantly broaden potential applications of Weyl semimetals.Here,we report a direct observation of robust edge states on atomic-scale ledges in TaAs using low-temperature scanning tunneling microscopy/spectroscopy.Spectroscopic signatures and theoretical calculations reveal that the 1D Fermi arcs arise from the chiral Weyl points of bulk crystals.The crossover from 2D Fermi arcs to eventual complete localization on 1D edges was arrested experimentally on a sequence of surfaces.Our results demonstrate extreme robustness of the bulk-boundary correspondence,which offers topological protection for Fermi arcs,even in cases in which the boundaries are at the atomic-scale.The persistent 1D Fermi arcs can be profitably exploited in miniaturized quantum devices.

International Center for Quantum Materials,School of Physics,Peking University,Beijing 100871,China;Beijing Academy of Quantum Information Sciences,Beijing 100193,China;State Key Laboratory of Superlattices and Microstructures,Institute of Semiconductors,Chinese Academy of Sciences,Beijing 100083,China;CAS Center for Excellence in Topological Quantum Computation,University of Chinese Academy of Sciences,Beijing 100190,China;Collaborative Innovation Center of Quantum Matter,Beijing 100871,China

[1]Xiaohu Zheng;Qiangqiang Gu;Yiyuan Liu;Bingbing Tong;Jian-Feng Zhang;Chi Zhang;Shuang Jia;Ji Feng;Rui-Rui Du-.Observation of 1D Fermi arc states in Weyl semimetal TaAs)[J].国家科学评论（英文版）,2022(08):53-61

TaAs,ledges,profitably

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