2019/01/10 by Z. -C. Rao, Zhicheng Rao, Hang Li +39 · 384 citations
Physics and Astronomy · #Advanced Condensed Matter Physics #Brillouin zone #Chiral anomaly #Chirality (physics) #Condensed matter physics #Fermi surface #Fermion #Nambu–Jona-Lasinio model #Physics #Physics of Superconductivity and Magnetism #Quantum mechanics #Quasiparticle #Spin (aerodynamics) #Superconductivity #Topological Materials and Phenomena #cond-mat.mes-hall #cond-mat.mtrl-sci
paper · pdf · doi:10.1038/s41586-019-1031-8
published in Nature 567(7749), 496-499 (Nature Portfolio) · This is the original version submitted to Nature on August 17, 2018. A revised version will appear in Nature
arxiv created 2019/01/10 · openalex publication_date 2019/03/01 · arxiv updated 2019/04/03 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
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.