1. Department of Physics, Harbin Institute of Technology, Harbin 150001, China
2. School of Mathematics and Physics, Suzhou University of Science and Technology, Suzhou 215009, China
3. Department of Physics, Soochow University, Suzhou 215123, China
4. College of Chemistry and Environment Science, Key Laboratory of Chemical Biology of Hebei Province, Hebei University, Baoding 071002, China