1. Institute
of Atomic and Molecular Physics, Sichuan University, Chengdu 610065, China
2. Department
of Physics, Nanyang Normal University, Nanyang 473061, China
3. Department
of Physics and High Pressure Science and Engineering Center, University of Nevada, Las Vegas, Nevada 89154, United States
4. Centre
for Science at Extreme Conditions and SUPA, School of Physics and
Astronomy, The University of Edinburgh, Edinburgh EH9 3JZ, United Kingdom