1. Department of Physics, Kyoto University, Kyoto 606-8502, Japan.
2. Department of Electrical Engineering, École de technologie supérieure (ÉTS), Montréal, Québec H3C 1K3, Canada.
3. Institute for Integrated Cell-Material Sciences (iCeMS), Kyoto University, Kyoto 606-8501, Japan.
4. Research Institute for Electronic Science, Hokkaido University, Hokkaido 001-0020, Japan.