Small anisotropy in iron-based superconductors induced by electron correlation

We have investigated the electron correlation effect on the electronic structures and transport properties of the iron-based superconductors using density functional theory (DFT) and dynamical mean field theory (DMFT). By considering the Fe 3d electron correlation using DMFT, the quasiparticle bandwidth near the Fermi level is found to be substantially suppressed compared to the conventional DFT calculation. Because of the different renormalization factors of each 3d orbital, DMFT gives considerably reduced electrical anisotropy compared to DFT results, which explains the unusually small anisotropic resistivity and superconducting property observed in the iron-based superconductors. We suggest that the electron correlation effect should be considered to explain the anisotropic transport properties of the general d/f valence electron system.

Figure 1

Orbital-resolved Fe 3d spectral functions of Ba(Fe${}_{0.9}$Co${}_{0.1}$)${}_2$As${}_2$ obtained with the DFT (blue lines) and DFT + DMFT methods (red lines).

Figure 2

The DFT + DMFT spectral function of Ba(Fe${}_{0.9}$Co${}_{0.1}$)${}_2$As${}_2$ (red spectrum) and rescaled DFT band structure (blue lines) by a factor of 2.5.

Figure 3

Schematic view of the electron correlation effect on the electrical anisotropy (γ${}_{\sigma }$). $v_i$ is the group velocity obtained from the band dispersion, and $Z_i$ is the band renormalization factor due to the electron correlation effect.

Figure 4

The experimental electrical anisotrop-ies[9, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44] of iron-based superconductors compared to the (a) DFT and (b) DFT + DMFT calculations. The dotted lines represent the reference points where the experimental and calculated results are in good agreements.