基金supported by National Science Foundation of China under Grant No. 10773008Sichuan Province Foundation for Fundamental Research under Grand No. 05JY029-092
基金The project supported by National Natural Science Foundation of China under Grant No. 10347008 and Science Foundation for Fundamental Research of Sichuan Province under Grand No. 05JY029-092. We would like to thank Prof. Zhang Jing-Yi and Dr. Ren Jun for their beneficial discussions.