1. Beijing National Laboratory for Condensed Matter Physics and Institute of Physics Chinese Academy of Sciences Beijing 100190 China
2. Department of Physics Hong Kong University of Science and Technology Hong Kong 999077 China
3. Songshan Lake Materials Laboratory Dongguan Guangdong 523808 China
4. School of Physical Sciences University of Chinese Academy of Sciences Beijing 100049 China
5. Department of Chemistry Hong Kong University of Science and Technology Hong Kong 999077 China