1. College of Physics, Sichuan University, Chengdu 610064, China
2. Institute for Micro and Nanotechnologies MacroNano(R) and Institute for Materials Science and Engineering, Chair of Materials for Electrical Engineering and Electronics, Technische Universität Ilmenau, 98693 Ilmenau, Germany
3. Department of Physics, Tsinghua University, Beijing 100084, P. R. China
4. Key Laboratory of High Energy Density Physics and Technology of Ministry of Education, Sichuan University, Chengdu 610065, China