1. Department of Applied Physics and Quantum Phase Electronics Center (QPEC), University of Tokyo, Bunkyo, Tokyo 113-8656, Japan
2. Division of Materials Phyasics, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan
3. RIKEN Center for Emergent Matter Science (CEMS), Wako, Saitama 351-0198, Japan
4. Tokyo College, University of Tokyo, Bunkyo, Tokyo 113-8656, Japan