基金This work was supported by the Natural Science Foundation of Anhui Province, China (No.1208085MD59), the National Natural Science Foundation of China (No.U1232209, No.41175121, and No.21307137), the Presidential Foundation of Hefei Institutes of Physical Science, Chinese Academy of Sciences, China (No.YZJJ201302), and the Knowledge Innovation Foundation of the Chinese Academy of Sciences (No.KJCX2-YW-N24).