Electronic and lattice dynamical properties of the iron-based superconductors LiFeAs and NaFeAs

TL;DR

This study investigates the electronic and lattice vibrational properties of LiFeAs and NaFeAs superconductors using density functional theory, revealing weak electron-phonon coupling and suggesting unconventional superconductivity.

Contribution

It provides detailed calculations of electronic structure and phonon frequencies, highlighting the insufficiency of electron-phonon coupling to explain superconductivity in these materials.

Findings

Density of states near Fermi level dominated by Fe 3d states

Electron-phonon coupling too weak to explain superconductivity

Indication of unconventional superconducting mechanism

Abstract

The electronic structure and lattice vibrational frequencies of the newly discovered superconductors, LiFeAs and NaFeAs, are calculated within density functional theory. We show that in the vicinity of the Fermi energy, the density of states is dominated by contributions from Fe 3d states. We also calculate the electron-phonon coupling strength and show that it is too weak to account for the observed values of the superconducting transition temperatures. This seems to indicate that the iron-based superconductors are not of the conventional type.