1. Department of Physics, University of Colorado—Boulder, Boulder, Colorado 43210, United States
2. U.S. Naval Research Laboratory, Washington, D.C. 20375, United States
3. U.S. Naval Academy, Annapolis, Maryland 21402, United States
4. Department of Chemical and Biomolecular Engineering, Rice University, Houston, Texas 77006, United States
5. Institute of Fundamental and Frontier, Sciences, University of Electronic Science and Technology of China, Chengdu 610054, P. R. China