1. Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, United States
2. Department of Chemistry, Wayne State University, Detroit, Michigan 48202, United States
3. Department of Physics, Wayne State University, Detroit, Michigan 48201, United States
4. Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027, United States
5. Department of Condensed Matter Physics and Materials Science, Brookhaven National Laboratory, Upton, New York 11973, United States