1. Departement of Physics, School of Science, Lanzhou University of Technology 1 , Lanzhou 730050, People’s Republic of China
2. School of Physics, Ningxia University 2 , Yinchuan 750021, People’s Republic of China
3. School of Physics and Optoelectronic Engineering, Nanjing University of Information Science and Technology 3 , Nanjing 210044, People’s Republic of China