Multi-band effects in in-plane resistivity anisotropy of strain-detwinned disordered Ba(Fe$_{1-x}$Ru$_{x}$)$_{2}$As$_{2}$

TL;DR

This study investigates how disorder and strain affect in-plane resistivity anisotropy in Ba(Fe$_{1-x}$Ru$_{x}$)$_{2}$As$_{2}$, revealing a two-band transport mechanism and the distinct impact of magnetic/nematic order on different Fermi surface regions.

Contribution

It demonstrates that disorder suppresses anisotropy contributions from high mobility carriers, highlighting the role of different Fermi surface pockets in resistivity anisotropy.

Findings

Resistivity difference obeys Matthiessen rule in disordered samples.

High mobility carriers' anisotropy is negligible in disordered samples.

Magnetic/nematic order affects different Fermi surface regions differently.

Abstract

In-plane resistivity anisotropy was measured in strain-detwinned as-grown and partially annealed samples of isovalently-substituted $\mathrm{Ba(Fe_{1-x}Ru_{x})_{2}As_{2}}$ ($0<x \leq 0.125$) and the results were contrasted with previous reports on anneal samples with low residual resistivity. In samples with high residual resistivity, detwinned with application of strain, the difference of the two components of in-plane resistivity in the orthorhombic phase, $\rho_a -\rho_b$, was found to obey Matthiessen rule irrespective of sample composition, which is in stark contrast with observations on annealed samples. Our findings are consistent with two-band transport model in which contribution from high mobility carriers of small pockets of the Fermi surface has negligible anisotropy of residual resistivity and is eliminated by disorder. Our finding suggests that magnetic/nematic order has dramatically different effect on different parts of the Fermi surface. It predominantly affects inelastic scattering for small pocket high mobility carriers and elastic impurity scattering for larger sheets of the Fermi surface.