1. RIKEN, Center for Emergent Matter Science, Wako-shi, Saitama 351-0198, Japan.
2. Department of Physical Electronics and Quantum Nanoelectronics Research Center, Tokyo Institute of Technology, O-okayama, Meguro-ku, Tokyo 152-8552, Japan.
3. Department of Applied Physics, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.