title: Electron-hole symmetry and magnetic coupling in antiferromagnetic LaFeAsO.
abstract: When either electron or hole doped at concentrations x approximately 0.1, the LaFeAsO family displays remarkably high temperature superconductivity with Tc up to 55 K. In the most energetically stable Q-->M=(pi,pi,0) antiferromagnetic (AFM) phase comprised of tetragonal-symmetry breaking alternating chains of aligned spins, there is a deep pseudogap in the Fe 3d states centered at the Fermi energy arising from light carriers (m* approximately 0.25-0.33), and very strong magnetophonon coupling is uncovered. Doping (of either sign) beyond x approximately 0.08 results in heavy carriers per Fe (by roughly an order of magnitude) with a large Fermi surface. Calculated Fe-Fe transverse exchange couplings Jij(R) reveal that exchange coupling is strongly dependent on both the AFM symmetry and on the Fe-As distance.
authors.affiliation: Department of Physics, University of California Davis, Davis, California 95616, USA.
authors.forename: Z P
authors.initials: ZP
authors.lastname: Yin
authors.forename: S
authors.initials: S
authors.lastname: Lebègue
authors.forename: M J
authors.initials: MJ
authors.lastname: Han
authors.forename: B P
authors.initials: BP
authors.lastname: Neal
authors.forename: S Y
authors.initials: SY
authors.lastname: Savrasov
authors.forename: W E
authors.initials: WE
authors.lastname: Pickett