Light –controlled magnetism in 2D vanadium dichalchogenides and related semiconductors*

Atomically thin transition metal dichalcogenide (TMD) semiconductors hold enormous potential for modern optoelectronic devices, magnetic sensing, and quantum computing applications. By inducing long-range ferromagnetism (FM) in these semiconductors by stacking them with other magnetic TMDs or through the introduction of small amounts of a magnetic dopant, it is possible to extend their potential in emerging spintronic applications. Here, we demonstrate light-mediated, room temperature (RT) FM in V-doped WS₂ (V-WS₂) and V-WSe₂ monolayers and in VSe₂/TS₂ (T=Mo, W) heterostructures. In our work, we developed a novel, ultrasensitive magnetometer using the principle of magneto-LC resonance, which employs a soft ferromagnetic microwire coil driven near resonance. This allows us to probe real-time change in the magnetic permeability of a sample placed in the core of the coil, upon application of an external stimulus. Using this technique, we measured light intensity dependent magnetic permeability of V-WS₂ (V-WSe₂) monolayers subject to light illumination. The magnetic permeability of the monolayer is found to depend on laser intensity, confirming light control of RT magnetism in this 2D material. Guided by density functional theory calculations, we attribute this phenomenon to excess holes in the conduction and valence bands, and carriers trapped in magnetic doping states, which mediates the magnetization of the V-WS₂ (V-WSe₂) monolayer. We also used demonstrated light-mediated RT magnetism in VSe₂/MoS₂ or VSe₂/WS₂ heterostructures. This is attributed to photon absorption at the MoS₂ (WS₂) layer that generates electron-hole pairs, thus mediating their magnetization, an effect which is enhanced by confinement effects. These findings provide unique routes to exploit light-controlled FM at RT in 2D-TMD dilute magnetic semiconductors and their heterostructures and potentially establish a new subfield named “photo-spintronics”.