近日，南方科技大学的刘奇航&陈朝宇及其研究小组与日本广岛大学的Kenya Shimada以及中国科学院上海微系统与信息技术研究所的沈大伟等人合作并取得一项新进展。经过不懈努力，他们对共线反铁磁体中的手性狄拉克费米子进行研究。相关研究成果已于2023年12月8日在国际知名学术期刊《中国物理快报》上发表。

该研究团队运用角分辨光谱学测量方法，成功揭示了共线反铁磁体CoNb₃S₆费米表面的电子口袋的表面起源。通过结合中子衍射和第一性原理计算，研究人员提出了一个多域共线反铁磁构型，并证实了由手性狄拉克类费米子诱导的费米弧表面态的存在。这一研究提供了光谱证据，证明了CoNb₃S₆中特殊自旋对称性所引起的手性狄拉克类费米子的存在，为探索反铁磁体中非常规准粒子激发下的新涌现现象铺平了道路。

据悉，在狄拉克半金属中，无质量的狄拉克费米子具有零手性，导致表面态与拓扑平凡的表面态相连，从而使得异常霍尔效应消失。然而，最近有人预测在某些共线反铁磁体的非相对论极限中，存在一种手性“类狄拉克”费米子。这种费米子的色散表现为由自旋简并线性带形成的四重简并交叉点，并且具有拓扑保护的费米弧。这种特殊的手性费米子在增强的晶体群（即自旋空间群）的层次结构中受到隐藏的SU(2)对称性的保护，但至今尚未通过实验得到验证。

附：英文原文

Title: Chiral Dirac Fermion in a Collinear Antiferromagnet

Author: citation_authors citation_authors

Issue&Volume: 2023-12-08

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. 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 an 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 antiferromagnetic configuration, rendering 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.

DOI: 10.1088/0256-307X/40/12/126101

Source: https://cpl.iphy.ac.cn/10.1088/0256-307X/40/12/126101