1. Institute
of Atomic and Molecular Physics, Jilin University, Changchun 130012, P. R. China
2. Shanghai
Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, P. R. China
3. Beijing Computational Science Research Center, Beijing, P. R. China
4. Department
of Physics and Materials Science and Centre for Functional Photonics
(CFP), City University of Hong Kong, Hong Kong SAR, P. R. China