[1] RIKEN Inst Phys & Chem Res, Photodynam Res Ctr, Aoba Ku, Sendai, Miyagi 9800845, Japan
[2] Tohoku Univ, Inst Mat Res, Aoba Ku, Sendai, Miyagi 9808577, Japan
[3] Shizuoka Univ, Dept Elect & Elect Engn, Hamamatsu, Shizuoka 4328561, Japan
[4] Tokyo Inst Technol, Mat & Struct Lab, Midori Ku, Yokohama, Kanagawa 2268503, Japan
[5] Univ Tokyo, Inst Solid State Phys, Kashiwa, Chiba 2778581, Japan
[6] Tohoku Univ, Dept Phys, Aoba Ku, Sendai, Miyagi 9808578, Japan
[7] Natl Inst Mat Sci, Tsukuba, Ibaraki 3050044, Japan