1. Electron
Microscopy Laboratory, School of Physics, Peking University, Beijing 100871, China
2. Collaborative Innovation
Center of Quantum Matter, Beijing 100871, China
3. State Key Laboratory
of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054, China
4. Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
5. Brookhaven National Laboratory, Upton, New York 11973, United States
6. Department of Physics and Key Laboratory
of Artificial Micro- and Nano-structures of Ministry of Education, Wuhan University, Wuhan 430072, China
7. Department of Electrical and Computer Engineering, University of Nebraska-Lincoln, Lincoln, Nebraska 68588, United States
8. State Key Laboratory for Mesoscopic Physics,
School of Physics, Peking University, Beijing 100871, China
9. International Center for Quantum Materials,
School of Physics, Peking University, Beijing 100871, China