1. State Key Laboratory of Low Dimensional Quantum Physics and Department of Physics Tsinghua University Beijing 100084 P. R. China
2. Beijing National Laboratory for Condensed Matter Physics Institute of Physics Chinese Academy of Sciences Beijing 100190 P. R. China
3. Songshan Lake Materials Laboratory Guangdong 523808 P. R. China
4. NYU‐ECNU Institute of Physics NYU Shanghai Shanghai 200122 P. R. China
5. Key Laboratory of Polar Materials and Devices (MOE) and Department of Electronics East China Normal University Shanghai 200241 P. R. China
6. Electron Microscopy Laboratory and International Center for Quantum Materials School of Physics Peking University Beijing 100871 P. R. China
7. Materials Science Division Argonne National Laboratory Lemont IL 60439 USA
8. Advanced Photon Source Argonne National Laboratory Lemont IL 60439 USA
9. Collaborative Innovation Centre of Quantum Matter Beijing 100871 P. R. China
10. Department of Physics New York University New York NY 10003 USA
11. Frontier Science Center for Quantum Information Beijing 100084 P. R. China