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, Helmholtzstraße 20, Dresden 01069, Germany
4. Department of Electronic and Information Engineering, Harbin Institute of Technology, Shenzhen 518055, P. R. China
5. Material Systems for Nanoelectronics, Technische Universität Chemnitz, 09111 Chemnitz, Germany