Isotropic Quenched Disorder Triggers a Robust Nematic State in Electron-Doped Pnictides

TL;DR

This study uses computational models to show that isotropic quenched disorder from Fe substitution in electron-doped pnictides stabilizes a robust nematic state by primarily causing magnetic dilution, with minimal impact from Fermi Surface changes.

Contribution

It demonstrates that isotropic quenched disorder, rather than electronic doping alone, is the main factor stabilizing the nematic phase in electron-doped pnictides.

Findings

Disorder from Fe substitution reduces $T_N$ and $T_S$ temperatures.

A robust nematic state is stabilized primarily by magnetic dilution.

Fermi Surface changes have minimal effect on critical temperatures.

Abstract

The phase diagram of electron-doped pnictides is studied varying the temperature, electronic density, and isotropic quenched disorder strength by means of computational techniques applied to a three-orbital ($xz$, $yz$, $xy$) spin-fermion model with lattice degrees of freedom. In experiments, chemical doping introduces disorder but in theoretical studies the relationship between electronic doping and the randomly located dopants, with their associated quenched disorder, is difficult to address. In this publication, the use of computational techniques allows us to study independently the effects of electronic doping, regulated by a global chemical potential, and impurity disorder at randomly selected sites. Surprisingly, our Monte Carlo simulations reveal that the fast reduction with doping of the N\'eel $T_N$ and the structural $T_S$ transition temperatures, and the concomitant stabilization of a robust nematic state, is primarily controlled by the magnetic dilution associated with the in-plane isotropic disorder introduced by Fe substitution. In the doping range studied, changes in the Fermi Surface produced by electron doping affect only slightly both critical temperatures.