Realization of very large Dzyaloshinskii-Moriya interaction and skyrmion states in two-dimensional Janus manganese dichalcogenides

The Dzyaloshinskii-Moriya interaction (DMI), which only exists in noncentrosymmetric systems, is responsible for the formation of exotic chiral magnetic states. However, it is absent in most theoretically predicted and experimentally confirmed two-dimensional (2D) magnetic thin films so far. In this report, we perform first-principles calculations to demonstrate that significant DMI can be obtained in a series of Janus monolayers of manganese dichalcogenides MnXY (X/Y = S, Se, Te, X ≠ Y) in which the difference between X and Y on the opposites sides of Mn breaks the inversion symmetry. In particular, the DMI amplitudes of MnSeTe and MnSTe are comparable to those of state-of-the-art ferromagnet/heavy metal (FM/HM) heterostructures. Moreover, by performing Monte Carlo simulations, we find that the MnSeTe and MnSTe monolayers can host stable skyrmion states with the application of a moderate external magnetic field. The present results pave the way for new device concepts utilizing chiral magnetic structures in specially designed 2D ferromagnetic materials.