Spin-phonon coupling in the superconductor FeTe0.5Se0.5 from first-principles calculations

We present a first-principles pseudopotential study on the phonon structure and the electron–phonon (EP) interaction of superconductor FeTe0.5Se0.5 in both the nonmagnetic (NM) and striped antiferromagnetic (SAF) phases with the ordered and disordered structural models. The calculations give similar results for the two different structural models, implying that the superconductivity in FeTe0.5Se0.5 may be insensitive to the local atomic structure. Comparing the phonon behavior in the SAF phase with that in the NM phase, we find that the spin-lattice interaction can lead to the phonon softening and increase EP coupling constant λ by about 50%. This enhancement EP coupling may play an important role in the superconducting pairing, but this mechanism alone cannot explain the high Tc in superconductor FeTe0.5Se0.5.