1. Collaborative Innovation Centre of Advanced Microstructures, Laboratory of Solid-State Microstructures, School of Physics, Nanjing University, Nanjing 210093, People’s Republic of China
2. Jiangsu Key Laboratory for Artificial Functional Materials, and Collaborative Innovation Center of Advanced Microstructures, Department of Materials Science and Engineering, Nanjing University, Nanjing 210093, People’s Republic of China