1. The
State Key Laboratory of Refractories and Metallurgy, Wuhan University of Science and Technology, Wuhan 430081, China
2. Department
of Physics and Materials Science, City University of Hong Kong, Tat Chee
Avenue, Kowloon, Hong Kong China
3. Wuhan
National Laboratory for Optoelectronics (WNLO) School of Optical and
Electronic Information, Huazhong University of Science and Technology, Wuhan 430074, China