作者机构:[1]Department of Physics, Shanxi University, Taiyuan 030006, China
相关基金:Project supported by the National Natural Science Foundation of China (Grants Nos. 11004126 and 61275212), the Natural Science Foundation of Shanxi Province, China (Grant No. 2011021003-1), and the National Basic Research Program of China (Grant No. 2010CB923102).