1. State Key Laboratory of Low-Dimensional Quantum Physics and Department of Physics, Tsinghua University, Beijing,100084, P. R. China
2. Beijing Academy of Quantum Information Sciences, Beijing 100193, P. R. China
3. Research Center for Electronic and Optical Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
4. Research Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
5. Institute for Advanced Study, Tsinghua University, Beijing 100084, P. R. China
6. Frontier Science Center for Quantum Information, Beijing, 100084, P. R. China
7. School of Materials Science and Engineering, Beihang University, Beijing 100191, P. R. China
8. Max Planck Institute for the Structure and Dynamics of Matter, Center for Free Electron Laser Science, 22761 Hamburg, Germany
9. Collaborative Innovation Center of Quantum Matter, Beijing, 100084, P.R. China