1. Institute
of Theoretical Physics, Chinese Academy of Sciences, Zhong Guan Cun East Street 55 #, P.O. Box 2735, Beijing 100190, P. R. China
2. School
of Physical Sciences, University of Chinese Academy of Sciences, 19A Yuquan Road, Shijingshan District, Beijing 100049, P. R. China
3. Beijing
National Laboratory for Condensed Matter Physics and Key Laboratory
of Soft Matter Physics, Institute of Physics, Chinese of Academy of Sciences, Beijing 100190, P. R. China