Physical College, Beijing Institute of Technology, Beijing 100081;
Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, P.O. Box 603, Beijing 100190;
Center for Condensed Matter and Materials Physics, Beihang University, Beijing 100191;
Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, P.O. Box 603, Beijing 100190;
Center for Condensed Matter and Materials Physics, Beihang University, Beijing 100191;
Physical College, Beijing Institute of Technology, Beijing 100081;
Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, P.O. Box 603, Beijing 100190;
Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, P.O. Box 603, Beijing 100190;