1. School of Physics and Technology, and Key Laboratory of Artificial Micro/Nano Structures of the Ministry of Education, Wuhan University, Wuhan 430072, People's Republic of China
2. Science and Technology College, Hubei University for Nationalities, Enshi, 445000 Hubei, People's Republic of China
3. School of Electrical Engineering and Automation, Henan Polytechnique University, Jiaozuo, Henan, People's Republic of China