1. Key Laboratory of Materials Physics Anhui Key Laboratory of Nanomaterials and Nanotechnology CAS Center for Excellence in Nanoscience Institute of Solid State Physics Chinese Academy of Sciences Hefei 230031 P. R. China
2. Institute of Physical Science and Information Technology Anhui University Hefei Anhui 230601 P. R. China
3. Hefei National Laboratory for Physical Sciences at the Microscale University of Science and Technology of China Hefei Anhui 230026 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
6. Center for Multidimensional Carbon Materials Institute for Basic Science (IBS) Ulsan 44919 Republic of Korea