1. National Laboratory of Solid State Microstructures, College of Physics, Nanjing University, Nanjing 210093, China
2. School of Physics and Engineering, Henan University of Science and Technology, Luoyang 471023, China
3. National Laboratory of Solid State Microstructures and Department of Materials Science and Engineering, Nanjing University, Nanjing 210093, China
4. Department of Physics, Nanjing University of Information Science and Technology, Nanjing 210044, China
5. Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China