Department of Physics, Harbin Institute of Technology, Harbin 150001, China;
Department of Physics, Capital Normal University, Beijing 100048, China;
Institute of Microelectronics of Chinese Academy of Sciences, Beijing 100029, China;
Department of Physics, Capital Normal University, Beijing 100048, China;
Department of Physics, Capital Normal University, Beijing 100048, China;
Department of Physics, Harbin Institute of Technology, Harbin 150001, China;
Department of Physics, Capital Normal University, Beijing 100048, China;
Department of Physics, Harbin Institute of Technology, Harbin 150001, China;