1. Department of Chemistry, and Materials Science Division, Lawrence Berkeley National Laboratory, University of California, Berkeley, Berkeley, CA 94720, USA.
2. Department of Physics, City University of New York (CUNY)–City College of New York, New York, NY 10031, USA.
3. Department of Physics, University of California, Berkeley, Berkeley, CA 94720, USA.
4. Department of Physics, Peking University, Beijing, China.
5. Department of Chemical and Biomolecular Engineering, and Materials Science Division, Lawrence Berkeley National Laboratory, University of California, Berkeley, Berkeley, CA 94720, USA.
6. Fakultät Physik, Technische Universität Dortmund, D-44221 Dortmund, Germany.
7. CUNY–Graduate Center, New York, NY 10016, USA.