1. Organic Solid Laboratory, BNLMS, CMS & Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, P. R. China, http://www.iccas.ac.cn
2. Institute of Condensed Matter and Materials Physics, Department of Physics, Peking University, Beijing, 100871, P. R. China
3. Beijing Synchrotron Radiation Facility, Institute of High‐Energy Physics, Chinese Academy of Sciences, Beijing, 100047, P. R. China
4. Institute of Physics, Chinese Academy of Sciences, Beijing, 100190, P. R. China
5. National Centre for Nanoscience and Technology, Beijing, 100190, P. R. China