1. School of Physics, Shandong University, Jinan, Shandong, 250100, China
2. Max Planck Institute for Solid State Research, Stuttgart 70569, Germany
3. Institute of Physics, Chinese Academy of Sciences, Beijing, 100080, China
4. Center for Condensed Matter
Sciences, National Taiwan University, Taipei,
10617 Taiwan
5. Stanford Synchrotron
Radiation
Lightsource, SLAC National Accelerator Laboratory, Menlo Park, California 94025, United States
6. Department of Physics, Northeastern University, Boston, Massachusetts 02115,
United States
7. Laboratory
of Advanced Materials,
Department of Physics, Fudan University, Shanghai, 200438, China
8. Department of Chemistry, Utrecht University, 3584 CA Utrecht, The Netherlands