1. Research Center for Functional Materials, National Institute for Materials Sciences (NIMS), Namiki 1-1, Tsukuba, Ibaraki 305-0044, Japan
2. International Center for Materials Nanoarchitectonics (MANA), NIMS, Namiki 1-1, Tsukuba, Ibaraki 305-0044, Japan
3. JST-PRESTO, The Japan Science and Technology Agency, Tokyo 102-0076, Japan
4. Institute of Microelectronics and Frontier Science Center for Quantum Information, Tsinghua University, Beijing 100084, China