[1] Natl Tsing Hua Univ, Dept Phys, Hsinchu 300, Taiwan
[2] Konkuk Univ, Sch Phys, Div Quantum Phases & Devices, Seoul 143701, South Korea
[3] Natl Ctr Theoret Sci, Div Phys, Hsinchu 300, Taiwan
[4] KIAS, Sch Phys, Seoul 130722, South Korea
[5] Chonnam Natl Univ, Dept Phys, 300 Yongbong Dong, Gwangju 500757, South Korea