1. Department of Basic Science, University of Tokyo, 3-8-1 Komaba, Meguro-ku, Tokyo 153-8902
2. Department of Organic and Polymeric Materials, Graduate School of Science and Engineering, Tokyo Insutitute of Technology, O-okayama, Tokyo 152-8902
3. Institute for Solid State Physics, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581