Continuous Semiconductor-to-Half-Metal-to-Metal Transition in 1D/2D CuX2/CrBr3 Heterostructures via Anion Substitution and Interfacial Compression

Abstract Using first-principles calculations, we systematically investigate one-dimensional (1D) CuBr2 and CuCl2 chains and their mixed-dimensional heterostructures with two-dimensional (2D) ferromagnetic CrBr3, focusing on the interfacial coupling mechanism and the continuous electronic transition behavior. Both heterostructures form stable stacking configurations with preserved ferromagnetic ground states. By interfacial compression, the CuBr2/CrBr3 heterostructure undergoes a continuous semiconductor-to-half-metal-to-metal transition. Remarkably, the half-metallic state emerges within a narrow window between approximately 2.78 and 2.85 Å, while the CuCl2/CrBr3 heterostructure remains semiconducting under all compression strains. Charge density difference and projected band structure analyses reveal that compression enhances the Br-p and Cu-d orbital hybridization at the CuBr2/CrBr3 interface, pushing the Br-p-dominated spin-up valence band maximum across the Fermi level and closing the spin-up gap. For CuCl2/CrBr3, the Cl-p orbitals lie farther from the Fermi level due to Cl’s higher electronegativity, preventing gap closure. This work establishes halogen species as a key control parameter for interfacial half-metallicity, providing a design principle for engineering half-metallicity in mixed-dimensional heterostructures.