1. Department of Electrical and Computer Engineering, Bourns College of Engineering, University of California, Riverside, California 92521, USA
2. School of Electrical, Computer and Energy Engineering, Arizona State University, Tempe, Arizona 85281, USA
3. Department of Physics, Arizona State University, Tempe, Arizona 85287, USA
4. CENTERA Laboratories, Institute of High-Pressure Physics, Polish Academy of Sciences, Warsaw 01-142, Poland