Antiferromagnetically assisted electron-phonon coupling and spin-lattice interaction in Fe-based superconductors

TL;DR

This paper introduces a comprehensive ab-initio theoretical approach that accurately predicts superconducting transition temperatures in various Fe-based superconductors by incorporating electron-phonon coupling, antiferromagnetism, and spin-lattice interactions.

Contribution

It presents a novel ab-initio method that explicitly includes antiferromagnetism and spin-lattice interactions to improve Tc predictions in iron-based superconductors.

Findings

Accurately predicts Tc for multiple Fe-based superconductors.

Shows antiferromagnetism enhances electron-phonon coupling.

Reproduces doping dependence of Tc in key materials.

Abstract

We present a theoretical ab-initio approach that allows us to explicitly calculate the superconducting transition temperatures (Tc) of the iron-based superconductors of LaFeAsO1-xFx, SmFeAsO1-xFx, NdFeAsO1-xFx, Ba1-xKxFe2As2, FeSe and LiFeAs that fit perfectly with the experiments. We consider recent evidence that electron-phonon coupling may have been underestimated previously, and a prediction that antiferromagnetism can greatly enhance electron-phonon coupling through localized iron d orbitals. We then include the contribution of these localized orbitals in a McMillan formalism. In addition, we take into account the spin-lattice interaction between the spin-polarized electrons at the Fermi surface and the iron orbitals in combination with a modified exchange Hamiltonian involving a ferrimagnetic coupling between Fe and As. With this approach we can accurately calculate the Tc of FeSe (11 family), LiFeAs (111 family), LaFeAsO0.9F0.1 (1111 family) and BaFe2As2 (122 family) as a function of pressure. In addition, we also obtain the correct doping dependence of Tc of LaFeAsO0.9F0.1 (1111 family) and BaFe2As2 (122 family).