1. Department of Physics and Astronomy Institute of Applied Physics and Research Institute of Advanced Materials Seoul National University Seoul 151‐747 Republic of Korea
2. Research Center for Novel Epitaxial Quantum Architectures Seoul National University 1, Gwanak‐ro, Gwanak‐gu Seoul 08826 Republic of Korea
3. Department of Materials Science and Engineering Seoul National University 1, Gwanak‐ro, Gwanak‐gu Seoul 08826 Republic of Korea
4. Interdisciplinary Program in Brain Science College of Science Seoul National University 1, Gwanak‐ro, Gwanak‐gu Seoul 08826 Republic of Korea