1. Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
2. School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
3. Center for Nanochemistry, Beijing Science and Engineering Centre for Nanocarbons, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
4. Institutes of Physical Science and Information Technology, Anhui University, Hefei 230601, China
5. Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, China