Computational search for Dirac and Weyl nodes in f-electron antiperovskites*

We present the results of a computational search for three-dimensional (3D) Dirac materials in the scarcely studied group of lanthanide antiperovskites [1]. There is no photoemission data available for these materials. We calculate electronic structures using density functional theory which accounts for spin-orbit coupling and strong correlations. We identify massive bulk Dirac states close to the Fermi level in A₃BO, where A=Sm, Eu, Gd, Yb and B=Sn, Pb. The 3D Dirac nodes along the Γ-M direction originate from the band inversion of the cation and anion bands at the Γ point. This band inversion is also an indication of a topological crystalline insulator phase [2]. Most of the predicted materials display a finite magnetic moment due to unpaired electrons in the 4f shell. Specifically, in magnetic Eu₃BO the degeneracy of the Dirac nodes is lifted, leading to appearance of Weyl nodes. This offers intriguing possibilities of combining magnetism and Dirac/Weyl physics in pristine materials without doping or proximity effects.
[1] Pertsova et al., PRB 99 (20), 205126 (2019)
[2] Hsieh et al., PRB 90, 081112(R) (2014); Kariyado and Ogata, J. Phys. Soc. Jpn. 80, 083704 (2011)