Electronic structure-dependent magneto-optical Raman effect in atomically thin WS₂

Magneto-optical effect, such as Faraday rotation, magneto-optical Kerr and Zeeman effect, plays a fundamental role and has found extensive applications in condensed-matter physics. Two-dimensional transition metal dichalcogenides provide us an unprecedented platform for exploring abundant magneto-optical phenomena. Here we report such experiments that demonstrate the band structure-dependent magneto-optical Raman effect in atomically thin WS₂. Our experiments in conjunction with theoretical calculations uncover that the direct to indirect transition leads to distinct magneto-optical Raman effect between monolayer and bilayer/trilayer. We further quantitatively determine the optical mobility of carriers at different critical points of conduction band (K and Q points). In addition, our measurements reveal that not only the particular single-phonon mode A_1g(Γ) but also multiple phonon replica and phonons at the edges of Brillouin zone display electronic structure-dependent gigantic magneto-optical Raman effect. Our work establishes a firm basis for benchmarking a new microscopic quantum Raman scattering theory, and paves a way towards novel magneto-optical applications based on 2D semiconductors.