1. Department of Modern Mechanical EngineeringWaseda University 3‐4‐1 Okubo, Shinjuku‐ku Tokyo 169‐8555 Japan
2. Center for Emergent Matter Science (CEMS)RIKEN 2‐1 Hirosawa Wako Saitama 351‐0198 Japan
3. Thin‐Film Device LaboratoryRIKEN 2‐1 Hirosawa Wako Saitama 351‐0198 Japan
4. Electrical and Electronic Engineering and Information SystemsThe University of Tokyo 7‐3‐1 Hongo, Bunkyo‐ku Tokyo 113‐8656 Japan