1. School of Physics and Engineering, and Key Laboratory of Material Physics of Ministry of Education, Zhengzhou University, Zhengzhou, Henan 450052, China
2. High Temperature Ceramic Institute, School of Materials Science and Engineering, Zhengzhou University, Zhengzhou, Henan 450052, China
3. Department of Applied Physics, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China