1. Shanghai Key Laboratory of High Temperature Superconductors Shanghai Frontiers Science Center of Quantum and Superconducting Matter States Physics Department Shanghai University Shanghai 200444 P. R. China
2. The Singapore Synchrotron Light Source (SSLS) National University of Singapore Singapore 117603 Singapore
3. School of Science Hebei University of Technology Tianjin 300401 P. R. China
4. Department of Applied Physics Zhejiang University of Technology Hangzhou 310023 P. R. China
5. Department of Physics Faculty of Science National University of Singapore Singapore 117542 Singapore
6. Centre for Advanced 2D Materials and Graphene Research National University of Singapore Singapore 117546 Singapore
7. Institute of Materials Research and Engineering Agency for Science, Technology and Research (A∗STAR) 2 Fusionopolis Way Singapore 138634 Singapore
8. School of Physics Shandong University Jinan 250100 P. R. China
9. Departement Fysica Universiteit Antwerpen Groenenborgerlaan 171 Antwerpen B‐2020 Belgium
10. Department of Physics Zhejiang University Hangzhou 310027 P. R. China