1. Institute for Solid State Physics University of Tokyo Kashiwa Chiba 277‐8581 Japan
2. CREST Japan Science and Technology Agency Kawaguchi Saitama 332‐0012 Japan
3. Department of Physics and Astronomy Johns Hopkins University Baltimore MD 21218 USA
4. RIKEN‐CEMS Wako Saitama 351‐0198 Japan
5. Institute of Physics Academia Sinica Taipei 115 Taiwan
6. Trans‐scale Quantum Science Institute University of Tokyo Bunkyo‐ku Tokyo 113‐0033 Japan
7. Department of Physics University of Tokyo Bunkyo‐ku Tokyo 113‐0033 Japan
8. Institute for Quantum Matter and Department of Physics and Astronomy Johns Hopkins University Baltimore MD 21218 USA