On the origin of non-monotonic doping dependence of the in-plane resistivity anisotropy in Ba(Fe$_{1-x}T_x$)$_2$As$_2$, $T$ = Co, Ni and Cu

TL;DR

This study investigates the non-monotonic doping dependence of in-plane resistivity anisotropy in Ba(Fe$_{1-x}T_x$)$_2$As$_2$ with T = Co, Ni, Cu, revealing how Fermi surface changes influence anisotropic transport properties.

Contribution

It provides new insights into how chemical substitution affects Fermi surface pockets and anisotropic resistivity in iron-based superconductors.

Findings

Resistivity anisotropy shows non-monotonic doping dependence.

Suppression of isotropic high mobility Fermi surface pocket correlates with increased anisotropy.

Magnetotransport measurements reveal non-linear Hall coefficient and linear transverse magnetoresistance.

Abstract

The in-plane resistivity anisotropy has been measured for detwinned single crystals of Ba(Fe$_{1-x}$Ni$_x$)$_2$As$_2$ and Ba(Fe$_{1-x}$Cu$_x$)$_2$As$_2$. The data reveal a non-monotonic doping dependence, similar to previous observations for Ba(Fe$_{1-x}$Co$_x$)$_2$As$_2$. Magnetotransport measurements of the parent compound reveal a non-linear Hall coefficient and a strong linear term in the transverse magnetoresistance. Both effects are rapidly suppressed with chemical substitution over a similar compositional range as the onset of the large in-plane resistivity anisotropy. It is suggested that the relatively small in-plane anisotropy of the parent compound in the spin density wave state is due to the presence of an isotropic, high mobility pocket of reconstructed Fermi surface. Progressive suppression of the contribution to the conductivity arising from this isotropic pocket with chemical substitution eventually reveals the underlying in-plane anisotropy associated with the remaining FS pockets.