1. Department of Materials Science and Engineering, Nanjing University, Nanjing 210093, China
2. High Magnetic Field Laboratory, Chinese Academic of Sciences, Hefei 230031, China
3. Department 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