[Zhou, Wei;Guo, Di;Huang, Guangming;Jin, Kai;Liu, Jun;Sun, Xiangming;Xiao, Le] Cent China Normal Univ, Coll Phys Sci & Technol, Wuhan 430079, Hubei, Peoples R China.^[Zhou, Wei;Gong, Datao;Sun, Quan;Liu, Chonghan;Liu, Tiankuan;Thomas, James;Ye, Jingbo] Southern Methodist Univ, Dept Phys, Dallas, TX 75205 USA.^[Qi, Ming] Nanjing Univ, Sch Phys, Nanjing 210008, Peoples R China.