Lifting the valley degeneracy in two-dimensional transition metal dichalcogenides could promote their applications in information processing. Various external regulations, including magnetic substrate, magnetic doping, electric field, and carrier doping, have been implemented to enhance the valley splitting under the magnetic field. Here, a phase engineering strategy, through modifying the intrinsic lattice structure, is proposed to enhance the valley splitting in monolayer WSe 2 . The valley splitting in hybrid H and T phase WSe 2 is tunable by the concentration of the T phase. An obvious valley splitting of ∼4.1 meV is obtained with the T phase concentration of 31% under ±5 T magnetic fields, which corresponds to an effective Landeǵ eff factor of −14, about 3.5-fold of that in pure H-WSe 2 . Comparing the temperature and magnetic field dependent polarized photoluminescence and also combining the theoretical simulations reveal the enhanced valley splitting is dominantly attributed to exchange interaction of H phase WSe 2 with the local magnetic moments induced by the T phase. This finding provides a convenient solution for lifting the valley degeneracy of two-dimensional materials.

In this work, a novel microwave hydrothermal method is developed to prepare hybrid 1T@2HÀ MoS 2 nanospheres, with the 1T and 2H phases confirmed by high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS) and the stability of the hybrid phase verified by Raman spectroscopy. The efficiencies of methyl orange (MO) degradation and photo-reduction of Cr(VI) by hybrid 1T@2HÀ MoS 2 are much higher than those by 2HÀ MoS 2 , which should be attributed to the synergistic effect of the coexistent 1T and 2H phases. In addition, the hybrid sample prepared by microwave method possesses superior photocatalytic performance than that by conventional hydrothermal method, due to the higher 1T phase concentration and different crystallinity. Free-radical capture experiments show that * O 2 À dominates the photocatalytic degradation process with 1T phase producing more electrons. The introduction of 1TÀ MoS 2 into 2HÀ MoS 2 shows great potential for photocatalytic degradation, while microwave treatment could be an effective method to prepare the hybrid phase MoS 2 . * OH to the improved photocatalytic activity were studied via control experiments by using hole and electron scavengers, proving that microwave hydrothermal treatment is a fast and easy synthetic method for producing high-quality MoS 2 .

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Two unequal K and K' valleys in transition metal dichalcogenides (TMDC) enable large and controllable polarization, which is the cornerstone of emerging valleytronic applications. Here, a phase engineering strategy aided by resonant plasmonic coupling is proposed to manipulate the valley degree of freedom. Compared with the pristine WSe2 monolayer, the hybrid H/T phase WSe2 exhibits an enhanced degrees of circular polarization (DCP) and valley polarization (DVP). As further aided by the designed Au plasmonic array, the T phase facilitates the excitons process and promotes the charge transfer in WSe2/Au interface under the plasmonic‐enhanced electromagnetic field. Consequently, both the DCP and DVP values are considerably enhanced to 38.5% (15.6%) and 15.1% (7.6%) at 13 K (room temperature), respectively. Through finite difference time domain simulations (FDTD), the near‐field excitation, exciton decay, and far‐field detection processes are systematically analyzed, and highly consistent polarizations are quantitatively achieved between the theoretical and the experimental results. Accordingly, the high polarizations are revealed to be contributed by the increased exciton generation and radiation efficiency, chiral electromagnetic field, and non‐equilibrium spin distribution in the hybrid phase. The research presented here illustrates a promising route to control the spin and valley degrees of freedom in TMDC materials.