1. School of Physics and National Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093, China
2. College of Physics Science and Technology, Yangzhou University, Yangzhou 225002, China
3. Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093, China
4. Department of Applied Physics, Zhejiang University of Technology, Xiaoheshan, Hangzhou 310023, China