1. Quantum-Phase Electronics Center and Department of Applied Physics; University of Tokyo; Tokyo 113-8656 Japan
2. RIKEN Center for Emergent Matter Science (CEMS); Wako 351-0198 Japan
3. National Institute of Advanced Industrial Science and Technology (AIST); Tsukuba 305-8562 Japan
4. Japan Synchrotron Radiation Research Institute (JASRI); Hyogo 679-5198 Japan
5. RIKEN SPring-8 Center; Hyogo 679-5148 Japan
6. Department of Advanced Materials Science; University of Tokyo; Kashiwa 277-8561 Japan