Fig. 1: Laser-induced demagnetisation processes and spin textures.

a Schematic of the ultrafast laser pulses with linear polarisation π on CrGeTe₃. b Evolution of the electronic (T_elec) and phonon (T_phon) temperatures using the 2TM approach after the application of a single pulse at different energy fluences (mJ cm⁻²). c Variation of the out-of-plane magnetisation M_z/M_s versus time (ps) at the fluences showed in b. Line breakings are used to separate the three regimes observed in the simulations. d–f Snapshots of the spin dynamics (M_z) following the pulse at 115 ps, 400 ps, and 8000 ps, respectively. A fluence of 0.14 mJ cm⁻² was used. g–i Local view of the spin textures with their respective topological number N_sk = + 1 (anti-skyrmion), −1 (skyrmion), and 0 (skyrmionium), respectively. The scale bar of 5 nm applies to both g and h. Skyrmions are generally more energetically stable than anti-skyrmions or skyrmionium even though both can stay for several nanoseconds and disappear as observed in our spin dynamics simulations.