1. State Key Laboratory of Functional Materials for Informatics Shanghai Institute of Microsystem and Information Technology Chinese Academy of Sciences Shanghai 200050 P. R. China
2. CAS Center for Excellence in Superconducting Electronics (CENSE) Shanghai 200050 P. R. China
3. Department of Materials Science and NanoEngineering Rice University Houston TX 77005 USA
4. School of Electronic, Electrical and Communication Engineering University of Chinese Academy of Sciences Beijing 100049 P. R. China
5. School of Physics and Electronics Central South University Changsha 410083 P. R. China
6. State Key Laboratory of Molecular Reaction Dynamics Dalian Institute of Chemical Physics Chinese Academy of Sciences Dalian 116023 P. R. China
7. School of Physical Science and Technology ShanghaiTech University Shanghai 200031 P. R. China