1. Department of Materials Science and Engineering National Yang Ming Chiao Tung University Hsinchu 30010 Taiwan
2. Department of Materials Science and Engineering National Chung Hsing University Taichung 40227 Taiwan
3. International Center for Quantum Materials School of Physics Peking University Beijing China
4. Electron Microscopy Laboratory School of Physics Peking University Beijing China
5. School of Advanced Materials and Nanotechnology Xidian University Xi'an 710126 China
6. Department of Physics Tsinghua University Beijing China
7. Department of Materials Science and Engineering The Pennsylvania State University University Park PA 16082 USA
8. Department of Materials Science and Engineering University of California Irvine CA 92697 USA
9. Department of Physics and Astronomy University of California at Irvine Irvine CA 92697 USA
10. Irvine Materials Research Institute University of California at Irvine Irvine CA 92697 USA
11. Department of Materials Science and Engineering Technion Israel Institute of Technology Haifa 3200003 Israel
12. Solid State Institute Technion Israel Institute of Technology Haifa 3200003 Israel
13. Department of Physics National Cheng Kung University Tainan Taiwan
14. Department of Materials Science and Engineering National Tsing Hua University Hsinchu 30013 Taiwan