1. Center for High Pressure Science and Technology Advanced Research (HPSTAR), P.O. Box 8009, Beijing 100088, China
2. School of Physics, Beijing Institute of Technology, Beijing 100081, China
3. Neutron Scattering Center (LANSCE), Los Alamos National Lab, Los Alamos, New Mexico 87545, USA
4. Physics Department, Southern University of Science and Technology, Shenzhen 518055, China