Observation of unconventional chiral fermions with long Fermi arcs in CoSi

Autor: Shangjie Tian, Junjie Li, Hechang Lei, Y. Huang, Zhi-Cheng Rao, Youguo Shi, Chen Fang, Hai Li, Chenghe Li, Youwen Long, Yujie Sun, Tiantian Zhang, B. B. Fu, Hongming Weng, Lin Wang, Cen-Yao Tang, Zhi Liu, Wenhui Fan, Z. L. Li, Hong Ding, Tian Qian
Rok vydání: 2019
Předmět:
Zdroj: Nature. 567:496-499
ISSN: 1476-4687
0028-0836
Popis: In condensed matter systems, chiral topological nodes are robust band crossing points in momentum space that carry nonzero Chern numbers. The chirality is manifested by the presence of surface Fermi arcs connecting the projections of nodes with opposite Chern numbers. In addition to the well-known Weyl nodes, theorists have proposed several other types of chiral topological nodes in condensed matter systems, but the direct experimental evidence of their existence is still lacking. Here, using angle-resolved photoemission spectroscopy, we reveal two types of new chiral nodes, namely the spin-1 nodes and charge-2 Dirac nodes, at the band crossing points near the Fermi level in CoSi, the projections of which on the (001) surface are connected by topologically protected surface Fermi arcs. As these chiral nodes in CoSi are enforced at the Brillouin zone (BZ) center and corner by the crystalline symmetries, the surface Fermi arcs connecting their projections form a non-contractible path traversing the entire (001) surface BZ, in sharp contrast to pairs of Weyl nodes with small separation. Our work marks the first experimental observation of chiral topological nodes beyond the Weyl nodes both in the bulk and on the surface in condensed matter systems.
Databáze: OpenAIRE
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