PHYSICAL REVIEW B 76, 064307 ，2007

Bo Liu,* Mu Gu, Zeming Qi, Xiaolin Liu,Shiming Huang, and Chen Ni
1Laboratory of Waves & Microstructure Materials, Pohl Institute of Solid State Physics, Tongji University, Shanghai 200092, China
2NSRL, University of Science and Technology of China, Hefei 230027, China