1. Ames National Laboratory, U.S. Department of Energy, Ames, IA 50011, USA
2. Department of Applied Physics, College of Science, Zhejiang University of Technology, Hangzhou, 310023, China
3. Jiyang College of Zhejiang Agriculture and Forestry University, Zhuji 311800, China
4. Department of Physics, Yantai University, Yantai 264005, China
5. Department of Physics and Astronomy, Iowa State University, Ames, IA 50011, USA
6. Department of Chemistry, Iowa State University, Ames, IA 50011, USA