1. Center for Nanophysics and Advanced Materials, University of Maryland, College Park, MD 20742, USA.
2. Department of Physics, University of Maryland, College Park, MD 20742, USA.
3. Ames Laboratory, Department of Physics and Astronomy, Iowa State University, Ames, IA 50011, USA.
4. Department of Physics, University of Central Florida, Orlando, FL 32816, USA.
5. Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
6. Condensed Matter Theory Center and Joint Quantum Institute, Department of Physics, University of Maryland, College Park, MD 20742, USA.
7. Department of Physics, University of Otago, P.O. Box 56, Dunedin 9054, New Zealand.
8. Department of Physics, University of Wisconsin, Milwaukee, WI 53201, USA.