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arXiv · 2301.12201

Chiral Dirac fermion in a collinear antiferromagnet

Ao Zhang·Ke Deng·Jieming Sheng·Pengfei Liu·Shiv Kumar·Kenya Shimada·Zhicheng Jiang·Zhengtai Liu·Dawei Shen·Jiayu Li·Jun Ren·Le Wang·Liang Zhou·Yoshihisa Ishikawa·Qiang Zhang·Garry McIntyre·Dehong Yu·Enke Liu·Liusuo Wu·Chaoyu Chen·Qihang Liu
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Abstract

In a Dirac semimetal, the massless Dirac fermion has zero chirality, leading to surface states connected adiabatically to a topologically trivial surface state as well as vanishing anomalous Hall effect (AHE). Recently, it is predicted that in the nonrelativistic limit of certain collinear antiferromagnets, there exists a type of chiral Dirac-like fermion, whose dispersion manifests four-fold degenerate crossing points formed by spin-degenerate linear bands, with topologically protected Fermi arcs. Such unconventional chiral fermion, protected by a hidden SU(2) symmetry in the hierarchy of an enhanced crystallographic group, namely spin space group, is not experimentally verified yet. Here, by angle-resolved photoemission spectroscopy measurements, we reveal the surface origin of the electron pocket at the Fermi surface in collinear antiferromagnet CoNb3S6. Combining with neutron diffraction and first-principles calculations, we suggest a multidomain collinear AFM configuration, rendering the the existence of the Fermi-arc surface states induced by chiral Dirac-like fermions. Our work provides spectral evidence of the chiral Dirac-like fermion caused by particular spin symmetry in CoNb3S6, paving an avenue for exploring new emergent phenomena in antiferromagnets with unconventional quasiparticle excitations.

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Ao Zhang, Ke Deng, Jieming Sheng, Pengfei Liu, Shiv Kumar, Kenya Shimada, Zhicheng Jiang, Zhengtai Liu, Dawei Shen, Jiayu Li, Jun Ren, Le Wang, Liang Zhou, Yoshihisa Ishikawa, Qiang Zhang, Garry McIntyre, Dehong Yu, Enke Liu, Liusuo Wu, Chaoyu Chen, Qihang Liu. 2023-01-28. Chiral Dirac fermion in a collinear antiferromagnet. https://doi.org/10.1088/0256-307x/40/12/126101

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