1. Department of Physics, Wuhan University, Wuhan 430072, People’s Republic of China
2. Department of Physics, Tsinghua University, Beijing 100084, People’s Republic of China
3. Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
4. Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee 37996, United States
5. ICQD, University of Science and Technology of China, Hefei, Anhui, People’s Republic of China