1. International Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan
2. JST-PRESTO, The Japan Science and Technology Agency, Tokyo 102-0076, Japan
3. Next Generation Semiconductor Group, National Institute for Material Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan
4. Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan
5. State Key Laboratory of Artificial Microstructure and Mesoscopic Physics, School of Physics, Peking University, Beijing, China