Magnetic-enhanced electron-phonon coupling and vacancy effect in 111-type iron pnictides from first-principle calculations

We investigate the lattice dynamics in both nonmagnetic and striped antiferromagnetic states of 111-type iron pnictides using the density-functional perturbation theory. The anisotropic spin-phonon effects lead to the softening of phonon frequencies and the renormalization of electronphonon matrix elements, so as to increase the electron-phonon couplings by 68%, 65%, and 0.9% for LiFeAs, NaFeAs, and LiFeP, respectively. Taking into account the vacancy effects in the three iron pnictides, we find that the electron-phonon couplings are further enhanced by hole doping, yielding superconducting transition temperatures close to their experimental values. 2012 American Institute of Physics. [doi:10.1063/1.3684710]