We have studied the newly found superconductor compound LaO1−xFxFeAs 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 2.3μB 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.
@article{arxiv.0803.3286,
title = {Iron-based layered superconductor LaO$_{1-x}$F$_x$FeAs: an antiferromagnetic semimetal},
author = {Fengjie Ma and Zhong-Yi Lu},
journal= {arXiv preprint arXiv:0803.3286},
year = {2008}
}