Stability and magnetism of strongly correlated single-layer VS2

Single-layer transition metal dichalcogenides exhibit a variety of atomic structures and associated exotic electronic and magnetic properties. Density-functional calculations using the LDA+U approximation show that single-layer VS2 is a strongly correlated material, where the stability, phonon spectra, and magnetic moments of the octahedral (1T) and the trigonal prismatic (2H) structures significantly depend on the effective Hubbard U parameter, Ueff. Comparison with the HSE06 hybrid density functional used as a benchmark indicates that Ueff=2.5 eV, which consistently shows that the 2H structure is more stable than the 1T structure and a ferromagnetic semiconductor. The magnetic moments are localized on the V atoms and coupled ferromagnetically due to the superexchange interactions mediated by the S atoms. Calculations of the magnetic anisotropy show an easy plane for the magnetic moment. Assuming a classical XY model with nearest neighbor coupling, we determine the critical temperature, Tc, for the Berezinsky-Kosterlitz-Thouless transition of 2H single-layer VS2 to be about 90 K. Applying biaxial tensile strains can increase Tc. Using Wannier interpolation, we evaluate the Berry curvature and anomalous Hall conductivity of 2H single-layer VS2. The coexistence of quasi-long-range ferromagnetic ordering and semiconducting behavior enables 2H single-layer VS2 to be a promising candidate for spintronics applications.