1. Condensed Matter Science and Technology, Institute and Department of Physics, Harbin Institute of Technology, Harbin 150080, People's Republic of China
2. Materials Research Institute and Department of Materials Science and Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802, USA
3. Pohang Accelerator Laboratory, Pohang University of Science and Technology, Pohang 790784, South Korea
4. Materials Research Institute and Department of Mathematics, Pennsylvania State University, University Park, Pennsylvania 16802, USA
5. Institute for Problems of Materials Science, National Academy of Science of Ukraine, 3, Krjijanovskogo, 03142 Kiev, Ukraine
6. Institute of Physics, National Academy of Sciences of Ukraine, 46, Nauki, 03028 Kiev, Ukraine
7. Rutgers Center for Emergent Materials and Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey 08854, USA