1. Tianjin Key Laboratory of Low Dimensional Materials Physics and Processing Technology, School of Science, Tianjin University, Tianjin 300350, China
2. School of Physics, The University of Sydney, Sydney, NSW 2006, Australia
3. Australian Centre for Microscopy & Microanalysis, The University of Sydney, Sydney, NSW 2006, Australia
4. Physical Science and Engineering Division, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia
5. Center for Joint Quantum Studies, School of Science, Tianjin University, Tianjin 300350, China