1. Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, U.K.
2. Faculty of Electrical Engineering and Electronics, Kyoto Institute of Technology, Matsugasaki,
Sakyo-ku, Kyoto 606-8585, Japan
3. Faculty of Materials Science and Engineering, Kyoto Institute of Technology, Matsugasaki,
Sakyo-ku, Kyoto 606-8585, Japan
4. Graduate School of Materials Science, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara 630-0192, Japan
5. Department of Applied Physics, Graduate School of Engineering, Osaka City University, Sugimoto, Sumiyoshi-ku, Osaka 558-8585, Japan