Unusual Dirac half-metallicity with intrinsic ferromagnetism in vanadium trihalide monolayers

Abstract

The Dirac half-metallicity (H. Ishizuka et al., Phys. Rev. Lett. 2012, 109, 237207, Li et al. Phys. Rev. B: Condens. Matter Mater. Phys., 2015, 92, 201403(R)) with a gap in one spin channel but a Dirac cone in the other has been proposed and attracted considerable attention. We report these exciting properties for VCl₃ and VI₃ layered materials based on density functional theory combined with the self-consistently determined Hubbard U approach (DFT+U_scf). Using DFT+U_scf, the stability and electronic and magnetic structures of VCl₃ and VI₃ monolayers are systematically investigated. The DFT+U_scf shows that VCl₃ and VI₃ monolayers have intrinsic ferromagnetism and half-metallicity. Remarkably, the VCl₃ and VI₃ monolayers possess a rather rare half-metallic Dirac point around the Fermi level with just one spin channel. In contrast to the Dirac point in graphene, the Dirac points in VCl₃ and VI₃ monolayers are mainly due to the V-d electrons and consequently they show a large spin–orbital coupling induced gaps of about 29 meV and 12 meV for VCl₃ and VI₃ monolayers, respectively. The Monte Carlo simulations based on the Ising model demonstrate that the Curie temperatures of VCl₃ and VI₃ sheets are only 80 K and 98 K, respectively. However, the Curie temperature can be increased up to room temperature by carrier doping. The feasibility of an exfoliation from VCl₃ and VI₃ layered bulk phases is confirmed due to the small cleavage energies. Our results greatly broaden the family of potential 2D Dirac materials. The calculated properties of VCl₃ and VI₃ monolayers show that these materials have great application potential, opening the way towards the development of high-performance electronic devices.