1. Nebraska Center for Materials and Nanoscience,
University of Nebraska, Lincoln, Nebraska 68588,
USA
2. Department of Physics and Astronomy, University of Nebraska, Lincoln, Nebraska 68588, USA
3. Ames Laboratory, US Department of Energy, Ames, Iowa 50011, USA
4. Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA
5. Key Laboratory of Material Physics, Institute of Solid State
Physics, Chinese Academy of Sciences, Hefei 230031,
People’s Republic of China
6. Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831,
USA
7. Chemical and Engineering Materials Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831,
USA