1. Key Laboratory of Colloid and Interface Chemistry; Ministry of Education; School of Chemistry and Chemical Engineering; Shandong University; Jinan 250100 P. R. China
2. International Center for Quantum Materials; and Electron Microscopy Laboratory; School of Physics; Peking University; Beijing 100871 P. R. China
3. State Key Laboratory of Advanced Welding and Joining; Harbin Institute of Technology; Harbin 150001 P. R. China
4. Collaborative Innovation Center of Quantum Matter; Beijing 100871 P. R. China