Analysis of spin-density wave conductivity spectra of iron pnictides in the framework of density functional theory

Johannes Ferber, Yu Zhong Zhang, Harald Olaf Jeschke, Roser Valentí

Research output: Contribution to journalArticle

25 Citations (Scopus)

Abstract

The optical conductivity of LaFeAsO, BaFe2 As2, SrFe2 As2, and EuFe2 As2 in the spin-density wave (SDW) state is investigated within density functional theory (DFT) in the framework of spin-polarized generalized gradient approximation (GGA) and GGA+U. We find a strong dependence of the optical features on the Fe magnetic moments. In order to recover the small Fe magnetic moments observed experimentally, GGA+ Ueff with a suitable choice of negative on-site interaction Ueff =U-J was considered. Such an approach may be justified in terms of an overscreening which induces a relatively small U compared to the Hund's rule coupling J, as well as a strong Holstein-type electron-phonon interaction. Moreover, reminiscent of the fact that GGA+ U eff with a positive Ueff is a simple approximation for reproducing a gap with correct amplitude in correlated insulators, a negative Ueff can also be understood as a way to suppress magnetism and mimic the effects of quantum fluctuations ignored in DFT calculations. With these considerations, the resulting optical spectra reproduce the SDW gap and a number of experimentally observed features related to the antiferromagnetic order. We find electronic contributions to excitations that so far have been attributed to purely phononic modes. Also, an orbital-resolved analysis of the optical conductivity reveals significant contributions from all Fe3d orbitals. Finally, we observe that there is an important renormalization of kinetic energy in these SDW metals, implying that the effects of correlations cannot be neglected.

Original languageEnglish
Article number165102
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume82
Issue number16
DOIs
Publication statusPublished - Oct 1 2010
Externally publishedYes

Fingerprint

Spin density waves
Group 5A compounds
Optical conductivity
Density functional theory
Iron
density functional theory
Magnetic moments
iron
conductivity
gradients
approximation
Electron-phonon interactions
Magnetism
Kinetic energy
magnetic moments
orbitals
Metals
electron phonon interactions
optical spectrum
kinetic energy

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Electronic, Optical and Magnetic Materials

Cite this

Analysis of spin-density wave conductivity spectra of iron pnictides in the framework of density functional theory. / Ferber, Johannes; Zhang, Yu Zhong; Jeschke, Harald Olaf; Valentí, Roser.

In: Physical Review B - Condensed Matter and Materials Physics, Vol. 82, No. 16, 165102, 01.10.2010.

Research output: Contribution to journalArticle

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