LIU Ning CUI Kun Huazhong University of Science and Technology,Wuhan.China DENG Zonggang Hefei University of Technology,Hefei,China CHENG Benpei KONG Jie Institute of Solid State Physics,Academia Sinica,Hefei,China Doctorate student,Department of Mechanical Engineering No.2,Huazhong University of Science and Technology,Wuhan 430074,China