1. Condensed Matter Science and Technology Institute and Department of Physics, School of Science, Harbin Institute of Technology, Harbin 150080, China
2. Electronic Materials Research Laboratory, Key Laboratory of the Ministry of Education, Xi’an Jiaotong University, Xi’an 710049, China
3. National Laboratory of Solid State Microstructures and Department of Materials Science and Engineering, Nanjing University, Nanjing 210093, China
4. Materials Research Institute and Department of Mathematics, The Pennsylvania State University, University
Park, State College, Pennsylvania 16802, United States