1. Institute of Semiconductors, South China Normal University, Guangzhou 510631, People's Republic of China
2. School of Physics, Northwest University, Xi'an 710069, China
3. Hunan Key Laboratory of Two-Dimensional Materials, Department of Applied Physics, School of Physics and Electronics, Hunan University, Changsha 410082, China
4. School of Physics and Optoelectronics, South China University of Technology, Guangzhou 510640, People's Republic of China
5. Songshan Lake Materials Laboratory, Dongguan 523808, China
6. China-Singapore International Joint Research Institute, Guangzhou Knowledge City, Guangzhou 510663, China