LaFeAsO$_{1-x}$F$_x$: A low carrier density superconductor near itinerant magnetism

TL;DR

This study uses density functional theory to analyze LaFeAsO$_{1-x}$F$_x$, revealing it as a low carrier density superconductor with high density of states near itinerant magnetism, influenced by doping levels.

Contribution

First detailed density functional analysis of LaFeAsO$_{1-x}$F$_x$ highlighting its proximity to magnetism and unique electronic properties among high $T_c$ superconductors.

Findings

Low carrier density and high density of states at $E_F$

Proximity to itinerant magnetism with magnetic fluctuations

Doping controls the balance between ferromagnetic and antiferromagnetic tendencies

Abstract

Density functional studies of 26K superconducting LaFeAs(O,F) are reported. We find a low carrier density, high density of states, $N(E_F)$ and modest phonon frequencies relative to $T_c$. The high $N(E_F)$ leads to proximity to itinerant magnetism, with competing ferromagnetic and antiferromagnetic fluctuations and the balance between these controlled by doping level. Thus LaFeAs(O,F) is in a unique class of high $T_c$ superconductors: high $N(E_F)$ ionic metals near magnetism.