1. Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Shenyang National Laboratory for Materials Science, School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China
2. Department of Physics, University of California at Berkeley, Berkeley, California 94720, United States
3. Department of Physics, Harvard University, Cambridge, Massachusetts 02138, United States
4. Department of Applied Physics, Stanford University, Stanford, California 94305, United States
5. Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States
6. Quantum and Electronic Materials Department, Sandia National Laboratories, Livermore, California 94550, United States
7. Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
8. International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
9. Department of Physics, Stanford University, Stanford, California 94305, United States
10. State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China
11. Institute for Nanoelectronic Devices and Quantum Computing, Fudan University, Shanghai 200433, China
12. Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
13. Kavli Energy NanoSciences Institute at the University of California, Berkeley, and Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States