[1] Dongguk Univ, Quantum Funct Semicond Res Ctr, Seoul 100715, South Korea
[2] Hanyang Univ, Quantum Funct Spin Lab, Seoul 133791, South Korea
[3] Hanyang Univ, Dept Phys, Seoul 133791, South Korea
[4] Hanyang Univ, Dept Mat Sci & Engn, Seoul 133791, South Korea
[5] Gyeongsang Natl Univ, Dept Phys, Jinju 660701, South Korea