1. School of Physics Science and Technology, Wuhan University, Wuhan 430072, People’s Republic of China
2. Division of Physics and Applied Physics, School of Physics and Mathematical Sciences, Nanyang Technological University, Singapore 637371, Singapore
3. School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798, Singapore
4. School of Physics, State Key Lab for Mesoscopic Physics, Peking University, Beijing 100871, People’s Republic of China
5. School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798, Singapore
6. CINTRA CNRS/NTU/THALES, UMI 3288, Research Techno Plaza, Singapore 637553, Singapore