1. Department of Physics and Astronomy, West Virginia University, Morgantown, West Virginia 26505, United States
2. Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey 08854, United States
3. Catalan Institute of Nanoscience and Nanotechnology (ICN2) and European Theoretical Spectroscopy Facility, CSIC and BIST,
Campus UAB, Bellaterra, 08193 Barcelona, Spain
4. Institute for Theoretical Solid State Physics, RWTH Aachen University, D-52056 Aachen, Germany
5. Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, New York 14853, United States
6. NanoMat/Q-Mat/CESAM and European Theoretical Spectroscopy Facility, Université de Liège (B5), B-4000 Liège, Belgium
7. Department of Physics and Materials Research Institute, The Pennsylvania State University, University Park, Pennsylvania 16802, United States