Low-temperature thermal conductivity of BaFe2As2: Parent compound of iron-arsenide superconductors

TL;DR

This study measures the low-temperature thermal conductivity of BaFe2As2, revealing contributions from electrons and phonons, consistent with a fully gapped magnon spectrum, and confirms the Wiedemann-Franz law at near-zero temperatures.

Contribution

First detailed low-temperature thermal conductivity measurements of BaFe2As2, linking electronic and phononic contributions and supporting a fully gapped magnon spectrum.

Findings

Thermal conductivity follows a T and T^{2.22} dependence at low temperatures.

Electronic contribution obeys Wiedemann-Franz law as T approaches 0 K.

Magnetic fields up to 8 T have minimal effect on thermal conductivity.

Abstract

We report low-temperature thermal conductivity down to 40 mK of the antiferromagnet BaFe$_2$As$_{2}$, which is the parent compound of recently discovered iron-based superconductors. In the investigated temperature range below 4 K, the thermal conductivity $\kappa$ is well described by the expression $\kappa$ = $aT$ + $bT^{2.22}$. We attribute the ``$aT$''-term to an electronic contribution which is found to satisfy the Wiedemann-Franz law in the $T$ $\to$ 0 K limit, and the remaining thermal conductivity, $\sim$ $T^{2.22}$, is attributed to phonon conductivity. A small influence on thermal conductivity by magnetic fields up to 8 T is well accounted by the observed magnetoresistance. The result is consistent with a fully gapped magnon spectrum, inferred previously from inelastic neutron scattering measurements.