[1] Fudan Univ, Dept Mat Sci, Shanghai 200433, Peoples R China
[2] Chinese Acad Sci, Hefei Inst Phys Sci, Inst Solid State Phys, Key Lab Mat Phys, Hefei 230031, Peoples R China
[3] Chinese Acad Sci, Hefei Inst Phys Sci, Inst Solid State Phys, Anhui Key Lab Nanomat & Nanostruct, Hefei 230031, Peoples R China
[4] Natl Inst Mat Sci, Opt & Elect Mat Unit, Tsukuba, Ibaraki 3050044, Japan
[5] Fudan Univ, Minist Educ, Key Lab Computat Phys Sci, Shanghai 200433, Peoples R China
[6] Fudan Univ, Dept Phys, Shanghai 200433, Peoples R China