[1] Natl Cheng Kung Univ, Dept Phys, Tainan 70101, Taiwan
[2] Natl Cheng Kung Univ, Ctr Quantum Frontiers Res & Technol QFort, Tainan 70101, Taiwan
[3] Xiangtan Univ, Minist Educ, Key Lab Low Dimens Mat & Applicat Technol, Xiangtan 411105, Hunan, Peoples R China
[4] Lund Univ, MAX IV Lab, S-22100 Lund, Sweden