[Chen, Xue-Kun; Chen, Ke-Qiu] Hunan Univ, Sch Phys & Elect, Dept Appl Phys, Changsha 410082, Hunan, Peoples R China.
[Chen, Xue-Kun] Univ South China, Sch Math & Phys, Hengyang 421001, Peoples R China.
[Chen, Chang-Yong] Shaoguan Univ, Dept Phys, Shaoguan 512005, Peoples R China.
[Liu, Jun] Cent S Univ, Coll Chem & Chem Engn, Changsha 410083, Hunan, Peoples R China.
[Chen, Ke-Qiu] Synerget Innovat Ctr Quantum Effects & Applicat H, Changsha 410081, Hunan, Peoples R China.