What controls the phase diagram and superconductivity in Ru substituted BaFe$_2$As$_2$?

TL;DR

This study investigates how Ru substitution affects the electronic structure and superconductivity in BaFe$_2$As$_2$, revealing that it does not alter the Fermi surface but likely suppresses magnetism through magnetic dilution.

Contribution

It demonstrates that Ru substitution in BaFe$_2$As$_2$ is isoelectronic and does not change the Fermi surface, suggesting a different mechanism for superconductivity emergence.

Findings

Ru substitution is isoelectronic with Fe.

No significant change in Fermi surface with Ru doping.

Superconductivity may be suppressed via magnetic dilution.

Abstract

We use high resolution angle-resolved photoemission to study the electronic structure of the iron based high-temperature superconductors Ba(Fe$_{1-x}$Ru$_x$)$_2$As$_2$ as a function of Ru concentration. We find that substitution of Ru for Fe is isoelectronic, i. e., it does not change the value of the chemical potential. More interestingly, there are no measured, significant changes in the shape of the Fermi surface or in the Fermi velocity over a wide range of substitution levels ($0<x<0.55$). Given that the suppression of the antiferromagnetic and structural phase has been associated with the emergence of the superconducting state, Ru substitution must achieve this via a mechanism that does not involve changes of the Fermi surface. We speculate that this mechanism relies on magnetic dilution which leads to the reduction of the effective Stoner enhancement.