1. State Key Laboratory for Mesoscopic Physics and Frontiers Science Center for Nano-Optoelectronics, School of Physics, Peking University, Beijing 100871, People's Republic of China
2. Collaborative Innovation Center of Quantum Matter, Beijing 100871, People's Republic of China
3. State Key Laboratory of Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Changchun 130012, People's Republic of China
4. Electron Microscopy Laboratory, School of Physics, Peking University, Beijing 100871, People's Republic of China
5. Institute of Physics, Otto-von-Guericke-University Magdeburg, Magdeburg 39106, Germany