1. College of Physics and Engineering, Chengdu Normal University 1 , Chengdu, Sichuan 611130, China
2. School of Physics and State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China 2 , Chengdu 610054, China
3. School of Physics and Optoelectronic Engineering, Yangtze University 3 , Jingzhou, Hubei 434023, China
4. School of Physics and Electronics, Central South University 4 , Changsha, Hunan 410083, China