First-principles study of Moiré excitons in a twisted 2D magnetic semiconductor

Recently, the moiré engineering of two-dimensional magnets is of particular interest for creating exotic quantum magnetic phases<span style="font-size:10.8333px">. Based on our recently developed noncollinear time-dependent density functional theory (TDDFT) methods, we performed a comprehensive study of the moiré magnetism and the spin-dependent moiré excitons in the twisted CrSBr bilayers. In contrast to the moiré superlattice without magnetism, where the moiré potential is mainly modulated by interlayer distance and structural reconstruction, the moiré potential in CrSBr shows significant spin dependence. With the twisted ferromagnetic (FM) spin configuration, one-dimensional moiré excitons can be trapped by the moiré potential in CrSBr moiré superlattice. However, with the twisted antiferromagnetic (AFM) spin configuratjion, the moiré exciton is much more delocalized due to shallow moiré potential. Under vertical electric field, the net magnetic moment of exciton becomes nonzero as the electron and hole separated into different layer. Compared with the untwisted CrSBr bilayer with FM interlayer coupling, the absorption peaks of the twisted CrSBr bilayer with FM coupling show blue shift and splitting, which can be used to identify these spin dependent moiré excitons.