Exploring YIG-induced magnetic proximity effect on the evolution of spin-polarized trion state in MoS2 monolayer

This study investigates the valley spin-polarization mechanisms in MoS₂ monolayers interfacing with a sputtered yttrium iron garnet (YIG) film. Structural and spectroscopic characterizations confirm successful MoS₂ monolayers transfer onto YIG with minimal strain issues but significant electron-doping effect, altering the exciton-trion population in MoS2. Temperature-dependent spin-resolved photoluminescence (SR-PL) measurements reveal both spin accumulation and Zeeman splitting contribute to valley spin-polarization below 50 K, as evidenced by intensity asymmetry and peak splitting in SR-PL spectra. However, as temperature increases to 50 K, characteristic on peak splitting vanishes, indicating that spin accumulation starts to dominate valley spin-polarization alone. A detailed temperature-dependent analysis further demonstrates that Zeeman splitting disappears above 40 K, while valley spin-polarization persists up to ~200 K, confirming that the magnetic proximity effect (MPE) induced spin accumulation at the trion state is the primary mechanism at elevated temperatures. The findings suggest that the MPE may play a crucial role in mediating the different trion configurations together with their symmetry-breaking. This work highlights the intricate interplay among spin accumulation, Zeeman splitting, and observed valley spin-polarization, opening an avenue toward future investigations utilizing gating techniques to control valley spin-polarization in two-dimensional materials.