High- TC superconductivity related to deep inner orbital coupling in FeAs-based compounds

The discovery of new iron-based high temperature superconductors REOFeAs (RE=La, Ce, Pr, etc.) led to a great deal of interest in study of superconductivity mechanism. The relation in electronic structure between arsenic atom and its nearest neighbor cation A for various Fe-As superconductor systems is studied. The result shows that the energy levels of 5p orbitals of all cation A occupy in a narrow energy extent of -14 to -26 eV, which are close to that of As 4s orbital. The calculated electronic structures show that there is an inner orbital coupling between As and near cation A. The distance of A-As has an approximately proportional relation with the critical temperature of superconductivity (TC). The larger intensity of the inner orbital coupling corresponds to the higher TC. We conclude the high- TC superconductivity originates from the inner orbital coupling between As and its near cation A atom for this kind of Fe-based REOFeAs superconductors. © 2009 American Institute of Physics.