1. Department of Applied Physics, Tokyo University of Science, Katsushika-ku, Tokyo 125-8585, Japan.
2. Department of Applied Physics and Quantum-Phase Electronics Center (QPEC), University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan.
3. Graduate School of Human and Environmental Studies, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan.
4. Condensed Molecular Materials Laboratory, RIKEN, Wako-shi, Saitama 351-0198, Japan.
5. Department of Physics, Toho University, Funabashi-shi, Chiba 274-8510, Japan.
6. Research Institute for Electronic Science, Hokkaido University, Kita-ku, Sapporo 001-0020, Japan.
7. Department of Applied Physics, University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan.