1. Wuhan National Laboratory for Optoelectronics and School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan, 430074, China
2. Beijing Institute of Nanoenergy and Nanosystems, Chinese Academy of Sciences, Beijing, China
3. Institute of Theoretical Physics and Key Laboratory for Magnetism and Magnetic Materials of MOE, Lanzhou University, Lanzhou 730000, China
4. School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0245, United States