作者机构:[1]Institute of Theoretical Physics, College qf Physics and Electronic Engineering, Northwest Normal University, Lanzhou 730070, China, [2]Department of Physics, North Carolina State University, Raleigh, NC, 27695-8202, USA
相关基金:Supported by National Natural Science Foundation of China (10547009) and Research Backbone Fostering Program of Knowledge and S&T Innovation Project of NWNU (KJCXGC 03-41)