Magnetic phase transition of monolayer RuCl₃ induced by optical and electrostatic unipolar doping

RuCl₃ is a layered material showing signatures of a quantum spin liquid and strong magnetic frustration. Based on first-principles calculations, we predict that electrostatic doping with either electrons or holes and optical doping can both cause a phase transition of free-standing monolayer RuCl₃ from the spin-liquid phase to stable ferromagnetic ordering with a moderate carrier/e-h density, achievable with current experimental techniques. Increasing the electron-hole pair density by optical doping can further enhance ferromagnetism and also increases the Curie temperature significantly. The mechanisms for driving the magnetic phase transition of monolayer RuCl₃ are discussed based on orbital magnetism and itinerant magnetism. Our prediction of optically driving 2D ferromagnetism offers the possibility of non-contact tunability for exploring new physics and spintronic applications.