1. Department of Electrical
and Computer Engineering, University of Minnesota, Minneapolis, Minnesota 55455, United States
2. Department of Physics, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
3. Department
of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, Minnesota 55455, United States
4. Department of Physics, California State University, Northridge, California 91330-8268, United States
5. Department of Physics and Astronomy, University of Delaware, Newark, Delaware 19716-2570, United States