1. Department of Basic Education, Qinghai University, Xining 810016, P. R. China
2. High Pressure Science and Engineering Center, University of Nevada, Las Vegas, Las Vegas, Nevada 89154, United States
3. Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065, P. R. China
4. Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, P. R. China
5. Academy for Advanced Interdisciplinary Studies, Southern University of Science and Technology, Shenzhen 518055, P. R. China