Electronic and Magnetic Properties of Vanadium-based Transition Metal Dichalcogenides: Quantum Monte Carlo and DFT+U Study

Two-dimensional vanadium-based dichalcogenides have attracted a great deal of attention due to their various electronic and optical properties depending on the composition of chalcogen atoms. We here present the results of our density functional theory (DFT) and quantum Monte Carlo (QMC) calculations for VX₂ and its janus structure VXY (X, Y=S and Te). For these layered materials, an accurate description of van der Waals interactions with QMC methods is highly desired for theoretical understanding of their electronic and magnetic properties. We first optimized the geometries of monolayers VS₂, VTe₂ and VSTe, which revealed that the DFT-PBE optimization calculations tend to overestimate their lattice parameters by ~ 4% when compared to the corresponding QMC results. Our PBE+U calculations with a QMC-optimized U value of 1.0 eV for vanadium showed stable antiferromagnetic ordering in the 1T phase of VTe₂ and VSTe, which is consistent with previous DFT studies. Finally, we discuss our QMC results for bilayer VX₂ and VXY, which allows us to examine the effects of the interlayer interactions on their electronic and magnetic properties.