1. Institute
for Solid State Physics, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581, Japan
2. COMP,
Department of Applied Physics, Aalto University, Otakaari 1, FI-00076 Helsinki, Finland
3. JST PRESTO, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan
4. Division
of Electrical Engineering and Computer Science, Kanazawa University, Kanazawa 920-1192, Japan
5. Department
of Chemistry, Kobe University, 1-1 Rokkodai, Nada, Kobe 657-8501, Japan