1. Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
2. University of Chinese Academy of Sciences, Beijing 100049, China
3. Department of Physics and Beijing Key Laboratory of Optoelectronic Functional Materials & Micro-nano Devices, Renmin University of China, Beijing 100872, China
4. Ames Laboratory, U.S. Department of Energy, Ames, Iowa 50011, United States
5. Department of Chemistry, Iowa State University, Ames, Iowa 50011, United States
6. School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
7. Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, China