Ultrafast Light-Induced Ferromagnetic State in Transition Metal Dichalcogenides Monolayers

Ultrafast optical control of magnetism had great potential to revolutionize magnetic storage technology and spintronics, but for now, its potential remains mostly untapped in two-dimensional (2D) magnets. Here, using the state-of-the-art real-time time-dependent density functional theory (rt-TDDFT), we demonstrate that an ultrafast laser pulse can induce a ferromagnetic state in nonmagnetic MoSe₂ monolayers interfaced with van der Waals (vdW) ferromagnetic MnSe₂. Our results show that the transient ferromagnetism in MoSe₂ derives from photoinduced direct ultrafast interlayer spin transfer from Mn to Mo via a vdW-coupled interface, albeit with a delay of approximately a few femtoseconds. This delay was strongly dependent on laser duration and interlayer coupling, which could be used to tune the amplitude and rate spin transfer. Furthermore, we have also shown that ferromagnetic states can be photoinduced in other transition metal dichalcogenides (TMDs), such as PtS₂ and TaSe₂ monolayers. Overall, our findings provide crucial physical insights for exploring light-induced interlayer spin and charge dynamics in 2D magnetic systems.