1. Condensed Matter Theory Laboratory, RIKEN, Wako, Saitama 351-0198, Japan
2. JST, CREST, Wako, Saitama 351-0198, Japan
3. Nanosystem Research Institute (NRI) “RICS”, AIST, Tsukuba, Ibaraki 305-8568, Japan
4. Advanced Institute for Computational Science, RIKEN, Kobe 650-0047, Japan
5. Department of Applied Physics, Tokyo University of Science, Shinjuku, Tokyo 162-8601, Japan
6. Research Institute for Science and Technology, Tokyo University of Science, Shinjuku, Tokyo 162-8601, Japan
7. JAIST, Nomi, Ishikawa 923-1292, Japan