1. National Laboratory of Solid State Microstructures, Jiangsu Key Laboratory of Artificial Functional Materials, College of Engineering and Applied Sciences, Nanjing University, Nanjing 210093, People’s Republic of China
2. Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, People’s Republic of China
3. School of Aerospace Engineering, Beijing Institute of Technology, Beijing 100081, People’s Republic of China
4. School of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing 210094, Jiangsu, People’s Republic of China
5. Department of Physics, University of Warwick, Coventry CV4 7AL, U.K.
6. Department of Physics and Astronomy, University of California, Irvine, California 92697, United States
7. Department of Materials Science and Engineering, University of California, Irvine, California 92697, United States
8. Irvine Materials Research Institute, University of California, Irvine, California 92697, United States