The magnetic proximity effect at the MoS2/CrI3interface.

The vicinity to a two-dimensional magnetic material provides a simple and effective way to break the valley degeneracy of transition-metal dichalcogenides because of the magnetic proximity effect. Based on first-principles calculations, we study the band structure of a MoS2/CrI3van der Waals heterostructure and its manipulation by vertical electric fields. A huge valley splitting of about 19.60 meV, equivalent to an external magnetic fields of about 89.0 T can be generated by an electric field of 0.115 V Å-1. The electric field causes discontinuous changes in the valley splitting. The electric field drives the bands of MoS2across those of CrI3. At the critical electric fields, the interlayer orbital hybridization leads to the energy level repulsion and an abrupt exchange of the band index. We also study the effect of interlayer distance on the valley splitting and observe a more significant electric field modulation. This work deepens our understanding on the interfacial magnetic proximity effect as a result of the orbital hybridization across the van der Waals gap.

Effects of pressure and strain on physical properties of VI3.

The van der Waals ferromagnetic material VI3is a magnetic Mott insulator. In this work, we investigate the effects of isotropic and anisotropic pressure on the atomic structure and the electronic structure of VI3using the first-principles method. The in-plane strain induces structural distortion and breaks the three-fold rotational symmetry of the lattice. Both the in-plane and out-of-plane strain widen the conduction and the valence bands, reduce the energy band gap and drive VI3from a semiconductor to a three-dimensional metal. The structural distortion is not the cause of insulator-to-metal transition. Calculations of the magnetocrystalline anisotropy energy indicate an easy-axis to easy-plane transition when the pressure is higher than 2 GPa. The ferromagnetic Curie temperature falls from 63 K at 0 GPa to 25 K at 6 GPa.