Distinct electronic nematicities between electron and hole underdoped iron pnictides

TL;DR

This study reveals distinct electronic nematic behaviors in electron- and hole-doped iron pnictides, showing different resistivity anisotropies and their relation to electronic states and orbital involvement.

Contribution

It provides the first systematic comparison of resistivity anisotropy and nematicity between electron- and hole-doped iron pnictides, highlighting fundamental differences in their electronic states.

Findings

Large anisotropy in electron-doped samples

Tiny anisotropy in hole-doped samples

Anisotropy linked to non-Fermi liquid behavior

Abstract

We systematically investigated the in-plane resistivity anisotropy of electron-underdoped $EuFe_{2-x}Co_xAs_2$ and $BaFe_{2-x}Co_xAs_2$, and hole-underdoped $Ba_{1-x}K_xFe_2As_2$. Large in-plane resistivity anisotropy was found in the former samples, while {\it tiny} in-plane resistivity anisotropy was detected in the latter ones. When it is detected, the anisotropy starts above the structural transition temperature and increases smoothly through it. As the temperature is lowered further, the anisotropy takes a dramatic enhancement through the magnetic transition temperature. We found that the anisotropy is universally tied to the presence of non-Fermi liquid T-linear behavior of resistivity. Our results demonstrate that the nematic state is caused by electronic degrees of freedom, and the microscopic orbital involvement in magnetically ordered state must be fundamentally different between the hole and electron doped materials.