Strain-tunable valley polarization and localized excitons in monolayer WSe<sub>2</sub>
Zheng Haihong, Biao Wu, Shaofei Li, Jun He, Zongwen Liu, Chang‐Tian Wang, Jian-Tao Wang, Ji’an Duan, Yanping Liu
Abstract
Monolayer transition metal dichalcogenides (TMDs) have a crystalline structure with broken spatial inversion symmetry, making them promising candidates for valleytronic applications. However, the degree of valley polarization is usually not high due to the presence of intervalley scattering. Here, we use the nanoindentation technique to fabricate strained structures of WSe 2 on Au arrays, thus demonstrating the generation and detection of strained localized excitons in monolayer WSe 2 . Enhanced emission of strain-localized excitons was observed as two sharp photoluminescence (PL) peaks measured using low-temperature PL spectroscopy. We attribute these emerging sharp peaks to excitons trapped in potential wells formed by local strains. Furthermore, the valley polarization of monolayer WSe 2 is modulated by a magnetic field, and the valley polarization of strained localized excitons is increased, with a high value of up to approximately 79.6%. Our results show that tunable valley polarization and localized excitons can be realized in WSe 2 monolayers, which may be useful for valleytronic applications.