[1] Univ Hong Kong, Dept Phys, Pokfulam Rd, Hong Kong, Hong Kong, Peoples R China
[2] Hong Kong Polytech Univ, Dept Elect & Informat Engn, Kowloon, Hong Kong, Peoples R China
[3] Univ Hong Kong, Dept Chem, Pokfulam Rd, Hong Kong, Hong Kong, Peoples R China
[4] South Univ Sci & Technol China, Dept Phys, Tangchang Rd, Shenzhen 518055, Guangdong, Peoples R China