Optical and Magneto-optical Characterizaiton of Vanadium Doped WS₂ and WSe₂ Monolayers

Two-dimensional dilute magnetic semiconductors have been realized in transition metal dichalcogenides doped with spin-polarized transition metals, such as vanadium-doped WS₂ and WSe₂ monolayers, which show room-temperature ferromagnetism. We performed power-dependent photoluminescence, resonant four-wave mixing, and differential reflectance spectroscopies on V-doped WS₂ at different doping levels. Instead of a single A exciton, doped samples display two peaks from donor-like states and the conduction band minima. Resonant Raman and SHG measurements reveal a blueshift in the B exciton but no shift in the C exciton. DFT calculations indicate the band structure strongly depends on the Hubbard U parameter for vanadium [1]. For V-doped WSe₂, magneto-PL experiments show giant effective g-factors (−27 to −69) for bound excitons at 4 K, which vanish at room temperature, suggesting magnetic ordering of vanadium impurity states. Ab initio calculations confirm this ordering and the resulting valence-band splitting at K and K′, consistent with our phenomenological model [2,3]. These findings highlight the potential of defect engineering in 2D materials for spintronic applications.

[1] Sousa et al., Adv. Opt. Mater. 2400235 (2024)

[2] Sousa et al., Small 2405434 (2024)

[3] Sousa et al., J. Phys. Chem. C 129, 8645–8653 (2025)