1. Department of Physics, Columbia University, New York, NY 10027, USA.
2. Department of Applied Physics and Applied Mathematics, Columbia University, New York, NY 10027, USA.
3. Department of Physics, University of California, Santa Barbara, CA 93106, USA.
4. National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan.
5. National High Magnetic Field Laboratory, Tallahassee, FL 32310, USA.