1. Department of Physics, Liaoning University, Shenyang 110036, China
2. Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
3. Songshan Lake Materials Laboratory, Dongguan 520838, China
4. Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China
5. Beijing Polytechnic College, Beijing 10042, China
6. Department of Applied Chemistry, Harbin Institute of Technology at Weihai, Weihai 264209, China