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

We report low-temperature thermal conductivity down to 40 mK of the antiferromagnet BaFe2As2, 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 -> 0 K limit and the remaining thermal conductivity, similar to 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.