Ultrafast laser-driven topological spin textures on a 2D magnet

Abstract The discovery of intrinsic magnetism in two-dimensional (2D) van der Waals (vdW) materials has opened the possibility to explore fundamental interactions between light, electron and spins at the atomic limit towards novel device architectures\cite{huang2017layer,Gong2017,GuguchiaSciAdv,wahab2021quantum,GuguchiaSantos,Wahab21,CantosPrieto2021,Alliati20,Genome22}. Ultrafast laser excitations provide an efficient and low-power consumption alternative since different magnetic features such as topological spin states can be triggered and manipulated at the femtosecond (fs) regime \cite{Carbone18,Ezawa13,Raising07,Beaurepaire09,Koopmans2010}. However, it is largely unknown whether laser excitations already used in data information platforms can manipulate the magnetic properties of 2D vdW magnets. Here we show that ultrashort laser pulses (30$-$85 fs) can not only manipulate magnetic domains of recently exfoliated 2D CrCl$_3$ ferromagnets\cite{Mcquire17}, but also induce the formation and control of topological nontrivial meron and antimeron spin textures. We observed that both spin quasiparticles are created within $\sim$100 ps after the excitation which determines on-demand their formation following the energy deposition into the system. Both merons and antimerons appear during the thermal equilibration and can generate a rich dynamics through motion, collision and annihilation with emission of spin waves. Our findings highlight substantial opportunities of using photonic driving forces for the exploration of spin textures on 2D magnetic materials towards magneto-optical topological applications.