1. Department of Physics, Tokyo Metropolitan University, Tokyo 192-0372, Japan
2. Department of Electrical and Computer Engineering, Rice University, Houston, Texas 77005, United States
3. Department of Liberal Arts, Faculty of Engineering, Tokyo University of Science, Katsushika, Tokyo 125-8585, Japan
4. Department of Physics and Astronomy, Rice University, Houston, Texas 77005, United States
5. Department of Material Science and NanoEngineering, Rice University, Houston, Texas 77005, United States