1. National Laboratory of Solid State Microstructures, School of Physics, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, China
2. Key Laboratory of Artificial Micro- and Nanostructures of the Ministry of Education, Hubei Nuclear Solid Physics Key Laboratory, School of Physics and Technology, Wuhan University, Wuhan 430072, China
3. College of Science, Southern University of Science and Technology, Shenzhen 518055, China