Gap Opening and Topological Phase Transition Induced by Sublattice Symmetry Breaking in Dirac Half-Metal PtBr _<b>3</b> via Heterostructure Interfacial Coupling

Two-dimensional (2D) materials, especially 2D magnetic materials, have attracted much attention due to their fascinating application prospects in spintronic devices and high-density storage equipment. For the core issue of efficient spin injection, highly spin-polarized half-metals are ideal alternative systems. Therefore, in this work, based on first-principles calculations, we focus on a Dirac half-metallic material, PtBr3, which not only retains the metallic property of a single spin channel but also has a Dirac electronic state near the Fermi level similar to that in graphene. Thus, it possesses both high spin polarization and a large carrier migration speed. The formation of the Dirac electronic state in this system stems from the inversion symmetry between the two magnetic Pt sublattices in the unit cell. Considering spin–orbit coupling (SOC), a 3.6 meV gap opening occurs at the Dirac state, and its topological properties and quantum anomalous Hall (QAH) characteristics have been proven. Interestingly, under the premise of lattice matching, two 2D semiconductors with different work functions, PtS2 and PtSe2, are selected to construct van der Waals (vdW) heterostructures with PtBr3. Through interfacial coupling, the sublattice inversion symmetry of PtBr3 can be disrupted, transforming it from a Dirac half-metal to a magnetic semiconductor with a trivial band gap or a traditional half-metal with a disturbed Dirac state but retaining a topological nature. Based on this behavior, a Dirac half-metallic field-effect transistor device with high spin injection efficiency is designed, providing a new approach for the development of high-density storage and new types of spin field-effect transistors.