Density functional study of FeS, FeSe and FeTe: Electronic structure, magnetism, phonons and superconductivity

摘要

We report density functional calculations of the electronic structure, Fermisurface, phonon spectrum, magnetism and electron-phonon coupling for thesuperconducting phase FeSe, as well as the related compounds FeS and FeTe. Wefind that the Fermi surface structure of these compounds is very similar tothat of the Fe-As based superconductors, with cylindrical electron sections atthe zone corner, cylindrical hole surface sections, and depending on thecompound, other small hole sections at the zone center. As in the Fe-As basedmaterials, these surfaces are separated by a 2D nesting vector at($\pi$,$\pi$). The density of states, nesting and Fermi surface size increasegoing from FeSe to FeTe. Both FeSe and FeTe show spin density wave groundstates, while FeS is close to an instability. In a scenario wheresuperconductivity is mediated by spin fluctuations at the SDW nesting vector,the strongest superconductor in this series would be doped FeTe.