[Ou, Congjie; Fang, Wei] Huaqiao Univ, Inst Syst Sci, Coll Informat Sci & Engn, Xiamen 361021, Peoples R China.
[Ou, Congjie; Fang, Wei] Huaqiao Univ, Dept Phys, Coll Informat Sci & Engn, Xiamen 361021, Peoples R China.
[Fang, Wei; Yang, Yaping] Tongji Univ, Sch Phys Sci & Engn, MOE Key Lab Adv Microstruct Mat, Shanghai 200092, Peoples R China.
[Li, Gao-xiang] Huazhong Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.