Coexistence of Spin-Polarized Dirac and Weyl Nodes in 2D Electride Ferromagnet Yttrium Iodide

Abstract

The unique electronic structure of yttrium iodide (YI) has been predicted for the first time, revealing nontrivial topological properties that combine spin-polarized Dirac and Weyl nodes within the same phase. The study identified nodal points present in both spin channels. The existence of Weyl nodes is further confirmed by the source and sink features in the Berry curvature plot and the presence of Fermi arcs in the surface band structure. The electron and hole packets are found to be connected at the Weyl point, classifying YI as a type-II magnetic Weyl semimetal. Under spin–orbit coupling (SOC), eight pairs of Weyl points exhibit robust behavior, while a small band gap forms at the spin-polarized Dirac cone. The system also demonstrates a high Fermi velocity, estimated at about 3.4 × 10⁵ m/s, for Dirac Fermions and a giant anisotropic intrinsic anomalous Hall conductivity of up to 933 S/cm.