[1] Nanjing Univ Sci & Technol, Dept Appl Phys, Nanjing 210094, Jiangsu, Peoples R China
[2] Anhui Polytech Univ, Dept Math & Phys, Wuhu 241000, Peoples R China
[3] Nanjing Univ Posts & Telecommun, New Energy Technol Engn Lab Jiangsu Prov, Nanjing 210023, Jiangsu, Peoples R China
[4] Nanjing Univ Posts & Telecommun, Sch Sci, Nanjing 210023, Jiangsu, Peoples R China