Giant Magneto-Exciton Coupling in 2D van der Waals CrSBr.

Controlling magnetic order via external fields or heterostructures enables precise manipulation and tracking of spin and exciton information, facilitating the development of high-performance optical spin valves. However, the weak magneto-optical signals and instability of two-dimensional (2D) antiferromagnetic (AFM) materials have hindered comprehensive studies on the coupling between magnetic order and excitons in bulk-like systems. Here, we leverage magneto-optical spectroscopy to provide direct insight into the spin-flip and complex spin-canting behavior in thick-layered CrSBr under nonextreme temperature conditions (80 K). Theoretical calculations reveal that the strong coupling between excitons and magnetic order, especially the 32 meV exciton energy shift during magnetic transitions, stems from the hybridization of Cr and S orbitals and the larger exciton wave function radius of higher-energy B excitons. These findings offer a solid foundation for future exploration of 2D AFM materials in magneto-optical sensors and quantum communication using excitons as spin carriers.