1. Laboratory of Nanostructure and Physics Properties, MOE Key Laboratory for Non-equilibrium Synthesis and Modulation of Condensed Matter, School of Science, Xi'an Jiaotong University, Shaanxi 710049, People's Republic of China
2. Department of Optical Information Science Technology, School of Science, Xi'an Jiaotong University, Shaanxi 710049, People's Republic of China
3. Department of Applied Physics, School of Science, Xi'an Jiaotong University, Shaanxi 710049, People's Republic of China