1. Department of Materials Science and Engineering, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan
2. RIKEN, Center for Emergent Matter Science (CEMS), Wako 351-0198, Japan
3. Research & Development Group, Hitachi Ltd., Hatoyama 350-0395, Japan
4. Institute of Multidisciplinary Research for Advanced Materials (IMRAM), Tohoku University, Sendai 980-8577, Japan