Role of electronic correlations in room-temperature ferromagnetism of monolayer MnSe2

The electronic structure of a two-dimensional ferromagnetic $\mathrm{Mn}{\mathrm{Se}}_{2}$ monolayer was investigated using density functional theory. It was found that the computed Curie temperature (${T}_{\mathrm{C}}$), which is fairly high but lower than room temperature, is sensitive to the on-site Coulomb repulsion $U$, indicating that electronic correlations have an important role in the magnetism exhibited in the system. The primary exchange mechanism responsible for the large ${T}_{\mathrm{C}}$ of monolayer $\mathrm{Mn}{\mathrm{Se}}_{2}$ was also clarified. Furthermore, it was demonstrated that the ${T}_{\mathrm{C}}$ can be enhanced up to nearly room temperature through charge doping and heterostructure engineering. These findings not only provide a fundamental understanding of the mechanism of magnetic ordering in $\mathrm{Mn}{\mathrm{Se}}_{2}$ monolayers, but also suggest a practical remedy for the enhancement of the ${T}_{\mathrm{C}}$ of $\mathrm{Mn}{\mathrm{Se}}_{2}$ by using various substrates, including Dirac materials.