Institution: | College of Physics, Hebei Normal University, Shijiazhuang 050016, China;Institute of Physics, Hebei University of Technology, Tianjin 300130, China College of Physics, Hebei Normal University, Shijiazhuang 050016, China College of Physics, Hebei Normal University, Shijiazhuang 050016, China Institute of Physics, Hebei University of Technology, Tianjin 300130, China |