1. Quantum-Phase Electronics Center and Department of Applied Physics, The University of Tokyo, Tokyo 113-8656, Japan
2. RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198, Japan
3. Okinawa Institute of Science and Technology Graduate University, Onna, Okinawa 904-0495, Japan
4. Materials Sciences Research Center, Japan Atomic Energy Agency, Sayo-gun, Hyogo 679-5148, Japan
5. Graduate School of Material Science, University of Hyogo, Kobe, Hyogo 678-1297, Japan