1. Department of Physics, Hebei Normal University, Shijiazhuang, 050024, P. R. China
2. Hebei Advanced Thin Films Laboratory, Shijiazhuang, 050024, P. R. China
3. College of Physics and Chemistry, Hebei Normal University of Science and Technology, Qinhuangdao, 066004, P. R. China
4. Institute of Applied Physics and Computational Mathematics, P.O. Box 8009, Beijing, 100088, P. R. China