[1] Korea Adv Inst Sci & Technol, Dept Nucl & Quantum Engn, Taejon 305701, South Korea
[2] Oak Ridge Natl Lab, Div Chem Sci, Oak Ridge, TN 37831 USA
[3] Korea Univ, Dept Phys, Seoul 136701, South Korea
[4] Chinese Acad Sci, Inst Solid State Phys, Hefei 230031, Peoples R China
[5] Zhengzhou Univ, Phys Sci & Technol Coll, Zhengzhou 450052, Henan, Peoples R China