[1] Fudan Univ, Dept Phys, Surface Phys Lab, Natl Key Lab, Shanghai 200433, Peoples R China
[2] Univ Hong Kong, Dept Phys, Hong Kong, Peoples R China
[3] Univ Sci & Technol China, Hefei Natl Lab Phys Sci Microscale, Anhua 230026, Peoples R China
[4] Hiroshima Univ, Grad Sch Sci, Hiroshima 7398526, Japan
[5] Renmin Univ China, Dept Phys, Beijing 100872, Peoples R China
[6] Chinese Acad Sci, Inst Phys, Beijing 100190, Peoples R China
[7] Fudan Univ, Adv Mat Lab, Shanghai 200433, Peoples R China
[8] Univ Sci & Technol China, Dept Phys, Anhua 230026, Peoples R China
[9] Hiroshima Univ, Hiroshima Synchrotron Radiat Ctr, Hiroshima 7398526, Japan