Drude weight anisotropy in the doped iron pnictides: the primary role of orbital weight redistribution along the reconstructed Fermi surfaces

TL;DR

This paper investigates how orbital weight redistribution along reconstructed Fermi surfaces influences Drude weight anisotropy in doped iron pnictides, revealing doping-dependent trends consistent with experiments.

Contribution

It demonstrates that orbital weight redistribution primarily drives conductivity anisotropy changes with hole doping in multiorbital models of pnictides.

Findings

Conductivity anisotropy decreases and reverses sign with hole doping.

Behavior is linked to orbital-resolved density of states and Fermi surface geometry.

Additional factors are needed to fully explain anisotropy in electron-doped regimes.

Abstract

We explore the anisotropy in low frequency conductivity as a function of hole doping in multiorbital models of pnictides by analyzing the Drude weight in the $x$ and $y$ directions of a ($\pi$, 0) spin-density wave state. A reduction in the conductivity anisotropy with increased hole doping, and subsequent sign reversal, both observed in experiments, is found to be a common trend in these models. This behavior arises due to the interplay of low energy orbitally-resolved density of states and the geometrical features of the Fermi surface. An understanding of anisotropy in the electron doped regime, however, would require additional ingredients.