Thermopower as sensitive probe of electronic nematicity in iron pnictides

TL;DR

This study demonstrates that thermopower anisotropy in EuFe$_{2}$(As$_{1-x}$P$_{x}$)$_2$ is a highly sensitive indicator of electronic nematicity, revealing anisotropic electronic behavior above phase transitions and sign changes linked to different underlying mechanisms.

Contribution

It provides new insights into electronic nematicity by showing thermopower anisotropy as a more sensitive probe than resistivity, highlighting the interplay of scattering and orbital polarization.

Findings

Thermopower anisotropy is more pronounced than resistivity anisotropy.

Thermopower anisotropy appears above structural and magnetic transitions.

Sign change in thermopower anisotropy occurs below the structural transition.

Abstract

We study the in-plane anisotropy of the thermoelectric power and electrical resistivity on detwinned single crystals of isovalent substituted EuFe$_{2}$(As$_{1-x}$P$_{x}$)$_2$. Compared to the resistivity anisotropy the thermopower anisotropy is more pronounced and clearly visible already at temperatures much above the structural and magnetic phase transitions. Most remarkably, the thermopower anisotropy changes sign below the structural transition. This is associated with the interplay of two contributions due to anisotropic scattering and orbital polarization, which dominate at high- and low-temperatures, respectively.