1. Beijing National Laboratory for Condensed Matter Physics, Institute
of Physics, Chinese Academy of Sciences, Beijing 100190, China
2. Collaborative Innovation Center of Quantum Matter, Beijing 100084, China
3. State Key Laboratory of Low-Dimensional
Quantum Physics and Department of Physics, Tsinghua University, Beijing 100084, China
4. Materials
Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
5. EM Business Unit, JEOL Ltd., Tokyo 196-8558, Japan
6. Department of Physics and Astronomy and
Department of Electrical Engineering and Computer Science, Vanderbilt University, Nashville, Tennessee 37235, United States
7. Hiroshima
Synchrotron Radiation Center, Hiroshima University, Kagamiyama
2-313, Higashi-Hiroshima 739-0046, Japan
8. Department of Materials
Science and Engineering, National University of Singapore, Singapore 117576 Singapore