1. Center for Integrated Nanotechnologies, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
2. Condensed Matter Theory Center and Joint Quantum Institute, University of Maryland, Baltimore, Maryland 20742, United States
3. Chemistry Division, Physical Chemistry and Applied Spectroscopy Group, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
4. Department of Physics, University of California at Berkeley, and Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States