College of Physics and Electronic Engineering Northwest Normal University Lanzhou 730070 China;
College of Physics and Electronic Engineering Northwest Normal University Lanzhou 730070 China;
School of Mathematics and Physics Lanzhou Jiaotong University Lanzhou 730070 China;
College of Physics and Electronic Engineering Northwest Normal University Lanzhou 730070 China;
College of Physics and Electronic Engineering Northwest Normal University Lanzhou 730070 China;
College of Physics and Electronic Engineering Northwest Normal University Lanzhou 730070 China;
Beijing National Laboratory for Condensed Matter Physics Institute of Physics Chinese Academy of Sciences Beijing 100190 China;
