1. Nanoscale Physics and devices Laboratory, Beijing National Laboratory for Condensed, Matter Physics and Institute of Physics; Chinese Academy of Sciences; Beijing 100190 China
2. Laboratory of Optical Physics, Beijing National Laboratory for Condensed Matter Physics and Institute of Physics; Chinese Academy of Sciences; Beijing 100190 China
3. SEU-FEI Nano-Pico Center, Key Laboratory of MEMS of Ministry of Education, School of Electrical Science and Engineering; Southeast University; 210096 Nanjing China