Magneto-elastic quantum fluctuations and phase transitions in the iron superconductors

TL;DR

This paper explores how magneto-elastic coupling influences magnetic and structural phase transitions in iron superconductors, explaining unusual magnetic ordering and structural transitions through quantum fluctuations.

Contribution

It introduces a model incorporating magneto-elastic interactions and quantum fluctuations to explain complex behaviors in iron superconductors, highlighting effects beyond mean-field approximations.

Findings

Iron telluride orders magnetically at a non-nesting wave-vector $(rac{\pi}{2}, rac{\pi}{2})$

Iron arsenides exhibit a $(\pi, 0)$ magnetic transition often preceded by an orthorhombic structural transition

Quantum fluctuations and magneto-elastic coupling are key to understanding these phenomena.

Abstract

We examine the relevance of magneto-elastic coupling to describe the complex magnetic and structural behaviour of the different classes of the iron superconductors. We model the system as a two-dimensional metal whose magnetic excitations interact with the distortions of the underlying square lattice. Going beyond mean field we find that quantum fluctuation effects can explain two unusual features of these materials that have attracted considerable attention. First, why iron telluride orders magnetically at a non-nesting wave-vector $(\pi/2, \pi/2)$ and not at the nesting wave-vector $(\pi, 0)$ as in the iron arsenides, even though the nominal band structures of both these systems are similar. And second, why the $(\pi, 0)$ magnetic transition in the iron arsenides is often preceded by an orthorhombic structural transition. These are robust properties of the model, independent of microscopic details, and they emphasize the importance of the magneto-elastic interaction.