1. Department of Physics, University of Washington, Seattle, WA 98195, USA.
2. Department of Physics, Carnegie Mellon University, Pittsburg, PA 15213, USA.
3. National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan.
4. Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
5. Department of Physics and Center of Theoretical and Computational Physics, University of Hong Kong, Hong Kong, China.
6. Department of Electrical Engineering, University of Washington, Seattle, WA 98195, USA.
7. Department of Materials Science and Engineering, University of Washington, Seattle, WA 98195, USA.