1. Key Lab of Microsystem and Microstructure of Ministry of Education; Harbin Institute of Technology; Harbin 150080 P. R. China
2. Department of Physics; Harbin Institute of Technology; Harbin 150080 P. R. China
3. Condensed Matter Science and Technology Institute; Harbin Institute of Technology; Harbin 150080 China
4. Academy of Fundamental and Interdisciplinary Science; Harbin Institute of Technology; Harbin 150080 China
5. Key Laboratory of Organic Solids; Institute of Chemistry; Chinese Academy of Sciences; Beijing 100190 P. R. China