Department of Physics, Lanzhou University of Technology, Lanzhou 730050, China;
Department of Physics, Lanzhou University of Technology, Lanzhou 730050, China;
Department of Physics, Lanzhou University of Technology, Lanzhou 730050, China;
Department of Physics, Lanzhou University of Technology, Lanzhou 730050, China;
Department of Physics, Lanzhou University of Technology, Lanzhou 730050, China;
State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, China;
