Iron-based layered superconductor LaO$_{1-x}$F$_x$FeAs: an antiferromagnetic semimetal

TL;DR

This study uses first-principles calculations to analyze LaO$_{1-x}$F$_x$FeAs, revealing its antiferromagnetic semimetal nature and suggesting a spin fluctuation-mediated mechanism for its superconductivity.

Contribution

It provides the first detailed theoretical analysis of LaO$_{1-x}$F$_x$FeAs, highlighting its antiferromagnetic properties and proposing a new mechanism for superconductivity.

Findings

LaOFeAs is an antiferromagnetic semimetal with electron carriers.

F-doping does not destroy the antiferromagnetic order.

Superconductivity likely mediated by spin fluctuations.

Abstract

We have studied the newly found superconductor compound LaO$_{1-x}$F$_x$FeAs through the first-principles density functional theory calculations. We find that the parent compound LaOFeAs is a quasi-2-dimensional antiferromgnetic semimetal with most carriers being electrons and with a magnetic moment of $2.3\mu_B$ located around each Fe atom on the Fe-Fe square lattice. Furthermore this is a commensurate antiferromagnetic spin density wave due to the Fermi surface nesting, which is robust against the F-doping. The observed superconduction happens on the Fe-Fe antiferromagnetic layer, suggesting a new superconductivity mechanism, mediated by the spin fluctuations. An abrupt change on the Hall measurement is further predicted for the parent compound LaOFeAs.