1. Center for High Pressure Science and Technology Advanced Research, Shanghai 201203, China
2. Department of Engineering Sciences and Mathematics, Luleå University of Technology, SE-97187 Luleå, Sweden
3. Department of Materials Science, Saarland University, Campus D3.3, D661-23 Saarbrücken, Germany
4. Department of Physics, Southern University of Science and Technology, Shenzhen, Guangdong 518055, China
5. Center for High Pressure Science (CHiPS), State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao, Hebei 066004, China
6. Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA