A topological Hund nodal line antiferromagnet

Tay-Rong Chang^1*

¹Physics, National Cheng Kung University, Tainan, Taiwan

* Presenter:Tay-Rong Chang, email:u32trc00@phys.ncku.edu.tw

Topological semimetals with protected band crossings have attracted intense interests recently. These non-trivial band crossings can exist close to the Fermi level in many 3D topological materials such as Weyl or Dirac semimetals with isolated degenerate points and nodal-line semimetals with 1D nodal loops. Still, the combination of magnetism, spin-orbit coupling, and topology in real materials is quite uncommon, especially antiferromagnetic topological materials. In this talk, I will introduce our recent finding on a fourfold degenerate Dirac nodal-line in an antiferromagnet YMn2Ge2 for the first time by using first-principles calculations [1]. We reveal that the Dirac nodal state in YMn2Ge2 is enforced to exhibit at the boundary lines of the Brillouin zone (BZ) by the combination of magnetism, space-time inversion, and nonsymmorphic lattice symmetry. This specific symmetry protection allows YMn2Ge2 to present the largest magnetic Dirac nodal-line in any real condensed matter system so far. Interestingly, the magnetic nodal line displays a d-orbital dependent renormalization along its trajectory in momentum space, thereby manifesting Hund’s coupling. Most importantly, our theoretical prediction was confirmed by ARPES. Our work thus identifies an important missing part in the topological family with magnetism.

[1] Xian P. Yang et al., A topological Hund nodal line antiferromagnet, Nature Communications 15, 7052 (2024).

Keywords: Topological materials, Nodal line, Antiferromagnetism, First-principles calculations