1. Department
of Physics and Astronomy, University of California, Irvine, California 92697-4575, United States
2. State Key Laboratory of Surface Physics and Key Laboratory for Computational Physical Sciences (MOE) & Department of Physics, Fudan University, Shanghai 200433, China
3. College
of Physics and Materials Science, Henan Normal University, Xinxiang, Henan 453007, China
4. Department
of Chemistry, University of California, Irvine, California 92697-2025, United States