[1] Wuhan Univ Technol, Sch Sci, Dept Phys, Wuhan 430070, Hubei, Peoples R China
[2] Wuhan Univ Technol, Sch Sci, Inst Condensed Matter Phys, Wuhan 430070, Hubei, Peoples R China
[3] Huazhong Univ Sci & Technol, Sch Phys, Wuhan 430074, Hubei, Peoples R China
[4] Tsinghua Univ, Dept Phys, Beijing 100084, Peoples R China