1. Beijing
National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
2. School
of Physics, Peking University, Beijing 100871, China
3. Collaborative Innovation Center of Quantum Matter, Beijing 100190, China
4. State
Key Laboratory of Low Dimensional Quantum Physics and Department of
Physics, Tsinghua University, Beijing 100084, P.R. China
5. Department
of physics, Renmin University of China, Beijing 100872, China
6. College
of Physics and Electronic Information, Gannan Normal University, Ganzhou, Jiangxi 341000, China
7. Beijing Key Laboratory for Nanomaterials and Nanodevices, Beijing 100190, China