1. Department of Physics, Korea Advanced Institute of Science and Technology (KAIST), Yuseong-gu, Daejeon 34141, Republic of Korea.
2. Center for Lattice Defectronics, KAIST, Yuseong-gu, Daejeon 34141, Republic of Korea.
3. Department of Physics, University of Seoul, Seoul 02504, Republic of Korea.
4. Graduate School of Nanoscience and Technology, KAIST, Yuseong-gu, Daejeon 34141, Republic of Korea.
5. Pohang Accelerator Laboratory, POSTECH, Pohang, Gyeongbuk 37673, Republic of Korea.
6. KAIST Institute for the NanoCentury, KAIST, Yuseong-gu, Daejeon 34141, Republic of Korea.