1. Department of Physics; National University of Singapore; Singapore 117542 Singapore
2. Center for advanced 2D materials; National University of Singapore; Singapore 117546 Singapore
3. School of Physics; Southeast University; Nanjing 211189 P.R. China
4. Department of Chemistry; National University of Singapore; Singapore 117543 Singapore
5. Ningbo Institute of Technology; Zhejiang University; Ningbo 31510 P.R. China
6. Institute for Advanced Study and Department of Physics; Nanchang University; Nanchang 330031 P.R. China
7. SZU-NUS Collaborative Innovation Center for Optoelectronic Science and Technology; Shenzhen University; Shenzhen 518060 P.R. China
8. Synergetic Innovation Center for Quantum Effects and Applications (SICQEA); Hunan Normal University; Changsha 410081 China
9. National University of Singapore (Suzhou) Research Institute; Su Zhou 215123 P.R. China