Optical Conductivity Anisotropy in the Undoped Three-Orbital Hubbard Model for the Pnictides

TL;DR

This study uses a three-orbital Hubbard model to explain resistivity anisotropy in undoped pnictides, revealing how orbital suppression and inter-orbital hopping influence conductivity differences.

Contribution

It introduces a mean-field approach to analyze orbital contributions to anisotropic conductivity in pnictides, highlighting the role of inter-orbital hopping suppression.

Findings

Conductance is higher along the antiferromagnetic direction.

Suppression of d_{yz} orbital at the Fermi surface affects conductivity.

Inter-orbital hopping suppression causes anisotropy.

Abstract

The resistivity anisotropy unveiled in the study of detwinned single crystals of the undoped 122 pnictides is here studied using the two-dimensional three-orbital Hubbard model in the mean-field approximation. Calculating the Drude weight in the x and y directions at zero temperature for a Q=(\pi,0) magnetically ordered state, the conductance along the antiferromagnetic direction is shown to be larger than along the ferromagnetic direction. This effect is caused by the suppression of the d_{yz} orbital at the Fermi surface, but additional insight based on the momentum dependence of the transitions induced by the current operator is provided. It is shown that the effective suppression of the inter-orbital hopping d_{xy} and d_{yz} along the y direction is the main cause of the anisotropy.