Magnetically-Driven Suppression of Nematic Order in an Iron-Based Superconductor

TL;DR

This paper investigates how magnetic fields influence nematic order in an iron-based superconductor, providing evidence that supports magnetically-driven models of nematicity through neutron diffraction experiments.

Contribution

The study presents neutron diffraction evidence of a four-fold symmetric phase near SDW suppression, supporting magnetically-driven nematic order models.

Findings

Observation of a four-fold symmetric phase near SDW suppression

Evidence supporting magnetically-driven nematic order models

Neutron diffraction confirms phase transition related to magnetic interactions

Abstract

A theory of superconductivity in the iron-based materials requires an understanding of the phase diagram of the normal state. In these compounds, superconductivity emerges when stripe spin density wave (SDW) order is suppressed by doping, pressure or atomic disorder. This magnetic order is often pre-empted by nematic order, whose origin is yet to be resolved. One scenario is that nematic order is driven by orbital ordering of the iron 3d-electrons that triggers stripe SDW order. Another is that magnetic interactions produce a spin-nematic phase, which then induces orbital order. In this article, we report the observation by neutron powder diffraction of an additional four- fold-symmetric phase in Ba1-xNaxFe2As2 close to the suppression of SDW order, which is consistent with the predictions of magnetically-driven models of nematic order.