1. National Laboratory of Solid State Microstructures Collaborative Innovation Center of Advanced Microstructures Nanjing University Nanjing 210093 China
2. College of Engineering and Applied Sciences Nanjing University Nanjing 210093 China
3. School of Physics Nanjing University Nanjing 210093 China
4. Department of Mathematics Nanjing University of Aeronautics and Astronautics Nanjing 210016 China
5. School of Electronic Science and Engineering Nanjing University Nanjing 210093 China