1. Institute
of Physics and Beijing National Laboratory for Condensed Matter Physics, Chinese Academy of Sciences, Beijing 100190, China
2. Beijing
National Laboratory for Molecular Sciences, College of Chemistry and
Molecular Engineering, Peking University, Beijing 100871, China
3. Research Center for Bioengineering and Sensing Technology, University of Science & Technology Beijing, Beijing 100083, China
4. National Center for Nanoscience and Technology, Beijing 100190, China