Abstract  

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 WSe2. The valley splitting in hybrid H and T phase WSe2 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 Landé geff factor of −14, about 3.5-fold of that in pure H-WSe2. 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 WSe2 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.

https://pubs.acs.org/doi/abs/10.1021/acsnano.0c08305

The related results were published in the internationally renowned journal ACS nano under the title "Enhanced Valley Splitting in Monolayer WSe2 by Phase Engineering" (ACS Nano 2021 15 (5), 8244-8251). The first authors of the paper are Ph.D. students Liu Haiyang and Associate Professor Fu Deyi from the School of Physical Science and Technology, Xiamen University. Assistant Professor Li Xu provided support for part of the sample testing. The corresponding authors are Professor Wu Yaping and Professor Wu Zhiming.