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

2010/05/31 by Johannes Ferber, Yu-Zhong Zhang, Yu‐Zhong Zhang +3 · 32 citations
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paper · pdf · doi:10.1103/physrevb.82.165102

published in Physical Review B 82(16) (American Physical Society) · 8 pages, 4 figures; recalculated spectra for U_eff=-1.9 eV for better comparison to experimental results, added discussion of the role of U and J in LDA+U

arxiv created 2010/08/02 · openalex publication_date 2010/10/01 · arxiv updated 2010/12/09 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05

Abstract

The optical conductivity of LaFeAsO, BaFe₂As₂, SrFe₂As₂, and EuFe₂As₂ 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+U_eff with a suitable choice of negative on-site interaction U_eff=U\ensuremath-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 U_eff is a simple approximation for reproducing a gap with correct amplitude in correlated insulators, a negative U_eff 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 Fe 3d 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.

Citations

• Correlated Electronic Structure ofLaO1−xFxFeAs
• Generalized Gradient Approximation Made Simple
• Competing orders and spin-density-wave instability in La(O 1−x F x )FeAs
• Electron-energy-loss spectra and the structural stability of nickel oxide: An LSDA+U study
• Multiband magnetism and superconductivity in Fe-based compounds
• Direct observation of the superconducting energy gap in the optical conductivity of the iron pnictide superconductorBa(Fe0.9Co0.1)2As2
• Anisotropy, Itineracy, and Magnetic Frustration in High-TCIron Pnictides
• Strong Correlations and Magnetic Frustration in the HighTcIron Pnictides
• Effects of magnetism and doping on the electron-phonon coupling inBaFe2As2
• Strong coupling between magnetic and structural order parameters inSrFe2As2
• In-plane electronic anisotropy in underdopedBa(Fe1−xCox)2As2revealed by partial detwinning in a magnetic field
• La claridad después de la lluvia: apuntes del natural para el viajero ilustrado y tranquilo
• Origin of the 150-K Anomaly in LaFeAsO: Competing Antiferromagnetic Interactions, Frustration, and a Structural Phase Transition

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• Accounting for spin fluctuations beyond local spin density approximation in the density functional theory
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