Light-induced ultrafast enhancement of magnetic orders in monolayer CrX3

Abstract

The recent discovery of light-tunable intrinsic ferromagnetism in two-dimensional (2D) van der Waals crystals has opened up a new arena for spintronics. However, the underlying mechanism is still under debate. Here, we performed excited-state density functional theory (DFT) calculations for optical manipulation of magnetism in monolayered CrX3 (X = Cl, Br, I). By applying the real-time time-dependent DFT method, we found that the laser pulses can directly induce ultrafast spin-selective charge transfer from X atoms to Cr atoms and further generate a dramatic magnetic moment of Cr atom changes. The microscopic mechanisms for ultrafast changing of magnetic order are discussed based on the p–d electron transition and electron–phonon coupling. Combined with constrained DFT and Monte Carlo simulations, we further theorized the light-excited effects on exchange interaction and found that the Curie temperature of CrX3 under light excitation (>150 K) is significantly higher than that in the ground state (<70 K). Our results open new opportunities to manipulate the spin in 2D magnets as well as the potential applications in spintronics.