1. Frontier Institute of Science and Technology, and State Key Laboratory
for Mechanical Behavior of Materials, Xi’an Jiaotong University, Xi’an 710049, People’s Republic of China
2. Department of Physics, University of Science and Technology of China, Hefei, Anhui 230026, People’s Republic of China
3. Department
of Nuclear Science and Engineering and Department of Materials Science
and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States