Do Transition Metal Substitutions Dope Carriers in Iron Based Superconductors?

TL;DR

This study uses first-principles calculations to show that transition metal substitutions in iron-based superconductors affect more than just carrier density, emphasizing the importance of disorder effects in understanding doping.

Contribution

It provides a detailed analysis of how disorder influences carrier properties in doped iron superconductors, beyond simple carrier counting methods.

Findings

Spectral weight reduction reduces coherent carrier density

Fermi surface changes do not directly indicate doping levels

Disorder effects are crucial in interpreting doping phenomena

Abstract

We investigate the currently debated issue concerning whether transition metal substitutions dope carriers in iron based superconductors. From first-principles calculations of the configuration-averaged spectral function of BaFe$_2$As$_2$ with disordered Co/Zn substitutions of Fe, important doping effects are found beyond merely changing the carrier density. While the chemical potential shifts suggest doping of a large amount of carriers, a reduction of the coherent carrier density is found due to the loss of spectral weight. Therefore, none of the change in the Fermi surface, density of states, or charge distribution can be solely used for counting doped coherent carriers, let alone presenting the full effects of the disordered substitutions. Our study highlights the necessity of including disorder effects in the studies of doped materials in general.