Phonon softening induced by striped antiferromagnetic order in LiFeAs

Using first-principles calculations in a supercell model with structural optimization, we investigate the magnetic ground state of LiFeAs and its phonon spectrum. The obtained magnetic ground state is the marginal striped antiferromagnetic state with partial structural relaxations. It is found that the anisotropic spin-lattice coupling in LiFeAs results in phonon softening of Fe-As atomic motion and so enhances the electron-phonon coupling. As a result, the electron-phonon interactions through the spin channel play an important role in the superconductivity of LiFeAs. (C) 2011 American Institute of Physics. [doi:10.1063/1.3555457]