1. Department of Mechanical and Aerospace Engineering, The Ohio State University, Columbus, OH 43210, USA.
2. Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.
3. Department of Electrical and Computer Engineering, North Carolina State University, Raleigh, NC 27606, USA.
4. Department of Materials Science and Engineering, North Carolina State University, Raleigh, NC 27606, USA.
5. Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6064, USA.
6. Department of Physics, The Ohio State University, Columbus, OH 43210, USA.
7. Department of Materials Science and Engineering, The Ohio State University, Columbus, OH 43210, USA.