1. Department of Physics, University of California San Diego, La Jolla, CA 92093
2. Center for High Pressure Science and Technology Advanced Research, Pudong, Shanghai 201203, People’s Republic of China
3. Univ Lyon, Université Claude Bernard Lyon 1, CNRS, Institut Lumière Matière, Villeurbanne 69100, France
4. State Key Laboratory of Surface Physics, Department of Physics, Fudan University, Shanghai 200433, People’s Republic of China
5. Shanghai Research Center for Quantum Sciences, Shanghai 201315, People’s Republic of China
6. Los Alamos National Laboratory, Los Alamos, NM 87545
7. University of California Irvine, Irvine, CA 92967