1. School of Physics, Southeast University, Nanjing 211189, P. R. China
2. Quantum Information Research Center, Southeast University, Nanjing 211189, P. R. China
3. Institute for Integrative Nanosciences, Leibniz IFW Dresden, Helmholtzstraße 20, Dresden 01069, Germany
4. Department of Electronic and Information Engineering, Harbin Institute of Technology (Shenzhen), Shenzhen 518055, P. R. China
5. Department of Physics, Department of Materials Science and Engineering, and Department of Biomedical Engineering, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong 999077, P. R. China
6. Material Systems for Nanoelectronics, Technische Universität Chemnitz, Chemnitz 09111, Germany