Importance of electronic correlations for structural and magnetic properties of the iron pnictide superconductor LaFeAsO

We present calculations of structural and magnetic properties of the iron-pnictide superconductor LaFeAsO including electron-electron correlations. For this purpose we apply a fully charge self-consistent combination of density-functional theory with the dynamical mean-field theory, allowing for the calculation of total energies. We find that the inclusion of correlation effects gives a good agreement of the arsenic $z$ position with experimental data even in the paramagnetic (high-temperature) phase. Going to low temperatures, we study the formation of the ordered moment in the striped spin-density-wave phase, yielding an ordered moment of about $0.60$${\mu }_{\mathrm{B}}$, again in good agreement with experiments. This shows that the inclusion of correlation effects improves both structural and magnetic properties of LaFeAsO at the same time.

Figure 1

The relative total energy of LaFeAsO as a function of the As height in the unit cell ($z$ parameter). Solid black line (triangles): LDA result. Red line (circles): LDA $+$ DMFT using FLL double counting. Blue line (diamonds): LDA $+$ DMFT using AMF double counting. Curves are shifted to give similar absolute value of the total energy. Vertical dashed line marks the experimental $z$ position. Error bars are calculated from averaging several further iterations at the self-consistent solution.

Figure 2

Magnetic properties of LaFeAsO in the paramagnetic (high-temperature) phase, calculated using AMF double-counting corrections. Upper panel: Local spin susceptibility for inverse temperatures (from top to bottom) $\beta =40$, 60, 80, and 100 eV${}^{-1}$, corresponding to temperatures $T=290$, 193, 145, and 116 K. Lower panel: Static susceptibility.

Figure 3

Spin dependent local density of states in the antiferromagnetic phase. Blue thin lines: LSDA. Red thicker lines: LDA $+$ DMFT using AMF double-counting correction.

Figure 4

Comparison of the self-energies for the $d_{xy}$ orbital for low Matsubara frequencies at $\beta =40$ eV${}^{-1}$. Dashed lines: one-shot non-self-consistent calculations. Solid lines: self-consistent calculations. Circles: FLL double counting. Crosses: AMF double counting.

Figure 5

Comparison of the $k$-summed spectral function for different LDA $+$ DMFT calculations. Black solid lines: LDA result. Green dot-dashed: LDA $+$ DMFT, FLL. Red dashed: LDA $+$ DMFT, AMF. Upper panel: non-self-consistent. Lower panel: self-consistent calculations.