Consecutive topological transitions of helical Fermi arcs at saddle points in CoSi
Science China Physics, Mechanics & Astronomy(2022)
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 CoSi. 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.
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关键词
topological transition,Fermi arcs,saddle point,73.20.At,68.37.-d,03.65.Vf
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