1. Nanophotonics and Optoelectronics Research Center, Qian Xuesen Laboratory of Space Technology, China Academy of Space Technology, Beijing 100094, P. R. China
2. Department of Physics and Institute of Materials Science and Engineering, Washington University, St Louis, Missouri 63130, United States
3. State Key Laboratory of Information Photonics and Optical Communications & School of Science, Beijing University of Posts and Telecommunications, Beijing 100876, P. R. China
4. State Key Laboratory for Mesoscopic Physics and School of Physics, Peking University, Beijing 100871, P. R. China
5. Collaborative Innovation Center of Quantum Matter, Beijing 100871, P. R. China
6. School of Advanced Materials, Peking University, Shenzhen Graduate School, Shenzhen 518055, P. R. China