Ultrafast Electron\nDynamics Dominated by Electron–Phonon\nCoupling in CrSBr Revealed by Photoemission Electron Microscopy

Layered semiconductor CrSBr has drawn much attention\ndue to its\ntwo-dimensional magnetic orders and strong multiphysics couplings.\nHerein, the electron dynamics of CrSBr (few layers to tens of nanometers)\nis investigated by time-resolved photoemission electron microscopy\nwith various photoexciting conditions. The valence electrons around\nthe Γ point are considered to be excited along the Γ-Y\ndirection and scattered with phonons along the nearly flat conduction\nband in the Γ-X direction. The relaxation lifetime of photoelectrons\ndecreases from ∼11 ps at 100 K to ∼2 ps at room temperature,\npresenting strong electron–phonon coupling in CrSBr. The lifetime\nis also found to be independent of pump polarization, which implies\nthat the excited-state electrons follow the identical relaxation channel,\nalthough CrSBr possesses great anisotropy.