[1] Shanghai Univ, Dept Elect Informat Mat, Shanghai 200444, Peoples R China
[2] Shanghai Univ, Dept Phys, Shanghai 200444, Peoples R China
[3] Univ Basque Country, Dept Quim Fis, Bilbao 48080, Spain
[4] Basque Fdn Sci, IKERBASQUE, Bilbao 48011, Spain