1. Department of Physics, Oregon State University, Corvallis, Oregon 97331-6507, United States
2. Department of Physics and Astronomy and
Center for Atomic Scale Electromagnetism, Seoul National University, Seoul 151-747, Republic of Korea
3. Photonic Systems Laboratory, School of EECS, Seoul National University, Seoul 151-744, Republic of Korea
4. Department of Physics and Department of Energy Systems Research, Ajou University, Suwon 443-749, Republic of Korea
5. Creative Research Center of Metal−Insulator Transition, Electronics and Telecommunications Research Institute, Daejeon 305-700, Republic of Korea
6. School of Advanced Device Technology, University of Science & Technology, Daejeon 305-333, Republic of Korea