1. Correlated Electron Research Center (CERC), National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8562
2. Department of Applied Physics, University of Tokyo, Tokyo 113-8656
3. RIKEN (The Institute of Physical and Chemical Research) and CREST-JST, Wako, Saitama 351-0198
4. Department of Advanced Materials, University of Tokyo, Kashiwa, Chiba 277-8561