1. Institute of Electrical Engineering, Chinese Academy of Sciences, Beijing 100190, China
2. Beijing National Laboratory of Condensed Matter Physics, Institute of Physics, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing 100190, China
3. Institut Jean Lamour, UMR 7198, CNRS-Université de Lorraine, BP239, 54506 Vandoeuvre-lès-Nancy, France