摘要
The CoSi family hosts unconventional topological nodes with nonzero Chern numbers.The nontrivial topology is manifested by conspicuous surface Fermi arcs connecting surface projections of the nodes.Here,using angle-resolved photoemission spectroscopy,we have systematically investigated the(001)surface states of pristine and Ni-doped Co Si.The surface states form saddle-like band structures at/near the time-reversal invariant point near the Fermi level.The Fermi arcs undergo consecutive Lifshitz transitions at the saddle points X,leading to changes of the Fermi arc configuration.As the density of states has a van Hove singularity at the saddle points,exotic many-body physical phenomena may emerge accompanied by the topological transitions of surface Fermi arcs.
基金
supported by the Ministry of Science and Technology of China(Grant Nos.2016YFA0401000,2016YFA0300600,2018YFE0202600,and 2016YFA0300504)
the National Natural Science Foundation of China(Grant Nos.U1832202,11774423,118224121,and 1888101)
the Chinese Academy of Sciences(Grant Nos.QYZDB-SSW-SLH043,XDB33020100,and XDB28000000)
the Beijing Natural Science Foundation(Grant No.Z200005)
the Fundamental Research Funds for the Central Universities and Research Funds of Renmin University of China(Grant Nos.18XNLG14,and 19XNLG17)
the Beijing Municipal Science and Technology Commission(Grant No.Z171100002017018)
support by the CAS Pioneer“Hundred Talents Program”(type C)。
