Abstract
In iron pnictides, we find that the moderate electron-phonon interaction due to the Fe-ion oscillation can induce the critical -orbital fluctuations, without being prohibited by the Coulomb interaction. These fluctuations give rise to the strong pairing interaction for the -wave superconducting (SC) state without sign reversal (-wave state), which is consistent with experimentally observed robustness of superconductivity against impurities. When the magnetic fluctuations due to Coulomb interaction are also strong, the SC state shows a smooth crossover from the -wave state with sign reversal (-wave state) to the -wave state as impurity concentration increases.
- Received 11 December 2009
DOI:https://doi.org/10.1103/PhysRevLett.104.157001
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