1. Key Laboratory of Materials Physics Anhui Key Laboratory of Nanomaterials and Nanotechnology CAS Center for Excellence in Nanoscience Institute of Solid State Physics HFIPS Chinese Academy of Sciences Hefei 230031 P. R. China
2. Department of Materials Science and Engineering University of Science and Technology of China Hefei 230026 P. R. China
3. Institute of Physical Science and Information Technology Anhui University Hefei 230601 P. R. China
4. Tsinghua University-Peking University Joint Center for Life Sciences School of Life Sciences Tsinghua University Beijing 100084 P. R. China
5. MOE Key Laboratory of Bioinformatics School of Life Sciences Tsinghua University Beijing 100084 P. R. China