Magnetic Proximity Coupling to Defects in a Two-Dimensional Semiconductor

The ultrathin structure and efficient spin dynamics of two-dimensional (2D) antiferromagnetic (AFM) materials hold promising opportunities for ultrafast memory devices, artificial intelligence circuits, and advanced computing technology. For example, chromium thiophosphate (CrPS₄) is one of the most promising 2D A-type AFM materials due to its robust stability in diverse environmental conditions and net out-of-plane magnetic moment in each layer, attributed to anisotropy in crystal axes (<i>a</i> and <i>b</i>). However, their net-zero magnetic moment poses a challenge for detecting the Néel state that is used to encode information. In this study, we demonstrate the detection of the Néel vector by detecting the magnetic order of the surface layer by employing localized defects in tungsten diselenide (WSe₂). These defects are ideal candidates for optically active transducers to probe the magnetic order due to their narrow line width and high susceptibility to magnetic field (<i>B</i>-fields). We observed spin-polarized charge transfer in the heterostructure of bulk CrPS₄ and single-layer WSe₂, indicating type-II band alignment as supported by density functional theory (DFT) calculations. In the A-type AFM regime, the intensity of both right-handed and left-handed circularly polarized light emanating from the sample remains constant as a function of the applied <i>B</i>-field, indicating a constant polarized transition behavior. Our results demonstrate an approach to optically characterizing the magnetic states of 2D bulk AFM material by using both localized and delocalized defect excitons as a probe, highlighting avenues for future research and technological applications.