1. Beijing National Laboratory for Condensed-Matter Physics and 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. School of Physics and Electronic Engineering, Jiangsu University, Zhenjiang, Jiangsu 212013, China
4. Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, China