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

TL;DR

This study uses density functional theory to analyze the electronic structure, magnetism, phonons, and potential superconductivity in FeS, FeSe, and FeTe, revealing similarities to Fe-As superconductors and insights into their magnetic and superconducting properties.

Contribution

It provides a comprehensive density functional analysis of FeS, FeSe, and FeTe, highlighting their electronic structures, Fermi surfaces, and magnetic states, and suggests spin fluctuations as a mechanism for superconductivity.

Findings

Fermi surface structures are similar to Fe-As superconductors.

FeSe and FeTe exhibit spin density wave ground states.

FeS is close to magnetic instability.

Abstract

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