[1] Sichuan Normal Univ, Dept Phys, Chengdu 610066, Peoples R China
[2] Sichuan Univ, Dept Phys, Chengdu 610065, Peoples R China
[3] Chinese Acad Sci, Inst Phys, Beijing 100080, Peoples R China
[4] Chinese Acad Sci, Ctr Condensed Matter Phys, Beijing 100080, Peoples R China