Photoexcitation induced magnetic phase transition and spin dynamics in antiferromagnetic MnPS3 monolayer

Abstract

Abstract Antiferromagnetic (AFM) spin dynamics is the key issue to develop innovative spintronic devices. Herein, we adopt ab initio nonadiabatic molecular dynamics with inclusion of spin-orbit-coupling (SOC) to investigate the photoinduced excitation of spin dynamics in MnPS3 monolayer as an AFM semiconductor. We find that optical doping can trigger MnPS3 from Néel AFM state to stable ferromagnetic (FM) phase with critical density of 1.11×1014 cm− 2 for electron-hole pairs, which is experimentally achievable. This phase transition can be ascribed to the optically induced mid-gap states of S-p orbitals, which lower the electron excitation energy and strengthen the SOC effect between S-p and Mn-d orbitals. For the nonequilibrium nonadiabatic coupling, the excited S-p electrons first decay to the mid-gap states due to p-p electron-phonon coupling and then relax to the spin-down Mn-d orbitals via SOC to recombine with holes. Such dramatic relaxation process not only prolongs the photogenerated carrier lifetime but also maintains the FM order for a long time up to 648 fs, which provides a possible explanation to the unusual optoelectronic performance of AFM MnPS3 monolayer. Excitingly, the reversible switching of magnetic order via optical means gives important clue for information storage and highly efficient photocatalysts by utilizing AFM semiconductors.