Spin-Phonon Coupling and Superconductivity in Fe Pnictides

TL;DR

This paper develops a phenomenological theory linking strong spin-lattice and spin-phonon interactions in iron pnictides to their superconductivity, suggesting electron-phonon coupling via spin channels plays a crucial role.

Contribution

It introduces a Landau theory based on DFT calculations and experiments to quantify spin-lattice coupling and its potential impact on superconductivity in Fe pnictides.

Findings

Strong spin-phonon coupling in Fe pnictides.

Spin-lattice interaction may significantly influence superconductivity.

Quantitative relation between magnetism and lattice effects.

Abstract

We propose a theory of strong spin-lattice and spin-phonon coupling in iron pnictides and discuss its implications on superconductivity. Strong magneto-volume effect in iron compounds has long been known as the Invar effect. Fe pnictides also exhibit this effect, reflected in particular to the atomic volume of Fe defined by the nearest neighbor atoms. Through the phenomenological Landau theory, developed on the basis of the calculations by the density functional theory (DFT) and the experimental results, we quantify the strength of the spin-lattice interaction as it relates to the Stoner criterion for the onset of magnetism. We suggest that the coupling between electrons and phonons through the spin channel may be sufficiently strong to be an important part of the superconductivity mechanism in Fe pnictides.