1. Department of Chemistry and Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials, Fudan University, Shanghai 200433, P. R. China
2. School of Microelectronics and State Key Laboratory of ASIC and System, Fudan University, Shanghai 200433, P. R. China
3. State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200438, P. R. China
4. School of National Defense Science and Technology, State Key Laboratory for Environment Friendly Energy Materials, Southwest University of Science and Technology, Mianyang 621010, China
5. Condensed Matter Theory Group, Materials Theory Division, Department of Physics and Astronomy, Uppsala University, Box 516, Uppsala 75120, Sweden
6. Yiwu Research Institute of Fudan University, Yiwu, Zhejiang 322000, P. R. China