1. School
of Physics and State Key Laboratory of Crystal Materials, Shandong University, Jinan, 250100, Shandong, China
2. Department of Electrical and Computer Engineering & Department of Physics, National University of Singapore, Singapore, 117579, Singapore
3. School
of the Gifted Young, University of Science and Technology of China, Hefei, 230026, Anhui, China
4. Department of Physics & Centre for Advanced Two-dimensional Materials, National University of Singapore, Singapore, 117542, Singapore
5. Department
of Materials Science and Engineering, University of Utah, Salt Lake City, Utah 84112, United States
6. Collaborative Innovation Center of Quantum Matter, Beijing, 100084, Beijing, China