1. The School of Mathematics and Physics, Jiangsu University of Technology, Changzhou 213001, China
2. School of Physics and Electronic Engineering, Zhengzhou Normal University, Zhengzhou 450044, China
3. Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093, China
4. Jiangsu Key Laboratory of Artificial Functional Materials, Department of Materials Science and Engineering, Nanjing University, Nanjing 210093, China