Manipulation of the excitonic emission in few-layer CrSBr by magnetic order, strain, and electrostatic doping

The two-dimensional (2D) magnetic material CrSBr has attracted significant interest for developing spin-based optoelectronic devices due to its unique magneto-optical properties. In this Letter, we report a systematic study on the photoluminescence (PL) of the high-energy excitons in few-layer CrSBr and the associated trions. Besides the broad excitonic emission peak (Xl) at around 1.34 eV, we also observed another strong excitonic emission peak (Xh) at around 1.37 eV in a hBN-encapsulated 2L sample, which splits into two peaks in 3L and more layered samples. The Xh exciton is associated with the transition between the top valence band and the second lowest conduction band, which is forbidden by inversion symmetry in 1L CrSBr. By applying inhomogeneous strain or constructing heterojunction, the Xh exciton can be brightened in 1L samples. In addition, we observed two trions associated with the split Xh excitons in electrostatically doped 3L CrSBr samples. By tuning the CrSBr sample into a ferromagnetic (FM) state, one of the trions shows enhanced intensity, which is more than 40 times that of the original exciton. Our results demonstrate that the excitonic emission in few-layer CrSBr can be effectively manipulated by magnetic order, strain, and electrostatic doping.