1. Department of Physics, University of Washington, Seattle, WA 98195, USA.
2. Department of Mechanical Engineering, Columbia University, New York, NY 10027, USA.
3. Department of Electrical Engineering, Columbia University, New York, NY 10027, USA.
4. National High Magnetic Field Laboratory, Tallahassee, FL 32310, USA.
5. Department of Physics, Carnegie Mellon University, Pittsburgh, PA 15213, USA.
6. National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan.
7. Department of Physics, Columbia University, New York, NY 10027, USA.
8. Department of Materials Science and Engineering, University of Washington, Seattle, WA 98195, USA.