1. SKLSM, Institute of Semiconductors, Chinese Academy of Sciences, P.O. Box 912, Beijing 100083, China
2. College of Materials Science and Optoelectronic Technology, University of Chinese Academy of Sciences, Beijing 100049, China
3. Department of Physics and State Key Laboratory of Surface Physics, Fudan University, Shanghai 200433, China
4. Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093, China
5. Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China