1. State Key Laboratory
for Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, China
2. Beijing
National Laboratory for Condensed Matter Physics, and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
3. Key Laboratory of Organic Optoelectronics
and Molecular Engineering of the Ministry of Education, Department
of Chemistry, Tsinghua University, Beijing 100084, China
4. State Key Laboratory of Silicon Materials,
Key Laboratory of Advanced Materials and Applications for Batteries
of Zhejiang Province, School of Materials Science and Engineering, Zhejiang University, Hangzhou, Zhejiang 310027, China
5. Department of Physics, University of California at Berkeley, Berkeley, California 94720, United States
6. Collaborative Innovation Centre of Quantum Matter, Beijing 100871, China