[1] Chinese Acad Sci, Shanghai Inst Opt & Fine Mech, Shanghai 201800, Peoples R China
[2] Chinese Acad Sci, Grad Sch, Beijing 100039, Peoples R China
[3] Chinese Acad Sci, Inst Solid State Phys, Key Lab Mat Phys, Hefei 230031, Peoples R China
[4] Chinese Acad Sci, Inst Solid State Phys, Anhui Key Lab Nanomat & Nanostruct, Hefei 230031, Peoples R China