Manifestations of multiple-carrier charge transport in the magnetostructurally ordered phase of undoped BaFe$_2$As$_2$

TL;DR

This study reveals multiple-carrier charge transport in the magnetostructurally ordered phase of undoped BaFe$_2$As$_2$, showing improved transport properties after annealing and evidence of at least three carriers contributing to conduction.

Contribution

It provides experimental evidence of multiple carriers with distinct properties in the ordered phase of BaFe$_2$As$_2$, aligning with recent quantum oscillation findings.

Findings

Annealing greatly reduces residual resistivity.

In-plane resistivity anisotropy diminishes after annealing.

Hall resistivity shows strong non-linearity, indicating multiple carriers.

Abstract

We investigated the transport properties of BaFe$_2$As$_2$ single crystals before and after annealing with BaAs powder. The annealing remarkably improves transport properties, in particular the magnitude of residual resistivity which decreases by a factor of more than 10. From the resistivity measurement on detwinned crystals we found that the anisotropy of the in-plane resistivity is remarkably diminished after annealing, indicative of dominant contributions to the charge transport from the carriers with isotropic and high mobility below magnetostructural transition temperature $T_{\rm s}$ and the absence of nematic state above $T_{\rm s}$. We found that the Hall resistivity shows strong non-linearity against magnetic field and the magnetoresistance becomes very large at low temperatures. These results give evidence for the manifestation of multiple carriers with distinct characters in the ordered phase below $T_{\rm s}$. By analyzing the magnetic field dependences, we found that at least three carriers equally contribute to the charge transport in the ordered phase, which is in good agreement with the results of recent quantum oscillation measurements.