Zeeman spectroscopy of excitons and hybridization of electronic states in few-layer WSe2, MoSe2 and MoTe2

Monolayers and multilayers of semiconducting transition metal dichalcogenides (TMDCs) offer an ideal platform to explore valley-selective physics with promising applications in valleytronics and information processing. Here we manipulate the energetic degeneracy of the K+ and K-valleys in few-layer TMDCs. We perform high-field magneto-reflectance spectroscopy on WSe2, MoSe2, and MoTe2 crystals of thickness from monolayer to the bulk limit under magnetic fields up to 30 T applied perpendicular to the sample plane. Because of a strong spin-layer locking, the ground state A excitons exhibit a monolayer-like valley Zeeman splitting with a negative g-factor, whose magnitude increases monotonically when crystal thickness decreases from bulk to a monolayer. Using kp calculations, we demonstrate that the observed dependence of g-factors for different materials is well accounted for by hybridization of electronic states in the K+ and K-valleys. The mixing of the valence and conduction band states induced by the interlayer interaction decreases the g-factor with increasing layer number. The effect is the largest for MoTe2, followed by MoSe2, and the smallest for WSe2.