Affiliation: | a Department of Physics, Southeast University, Nanjing 211189, China b Department of Materials Science and Engineering, Nanjing University, Nanjing 210008, China c School of Materials Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China d Department of Physics, Nanjing University, Nanjing 210008, China |