Enhanced Valley Splitting in Monolayer WSe 2 by Phase Engineering

• Published in: ACS nano Vol. 15; no. 5; pp. 8244 - 8251
• Main Authors: Liu, Haiyang, Fu, Deyi, Li, Xu, Han, Junbo, Chen, Xiaodie, Wu, Xuefeng, Sun, Baofan, Tang, Weiqing, Ke, Congming, Wu, Yaping, Wu, Zhiming, Kang, Junyong
• Format: Journal Article
• Language: English
• Published: United States 25.05.2021
• Subjects: valleytronics; phase transition; H phase; T phase; 2D transition metal dichalcogenides
• ISSN: 1936-0851; 1936-086X
• DOI: 10.1021/acsnano.0c08305

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