Inelastic Scattering on the Thermal Conductivity of Ba1−x K x Fe2As2

Abstract

The thermal conductivity of Ba1−xKxFe2As2 shows a large peak at a temperature somewhat below half the value of its superconducting state critical temperature Tc. A corresponding peak was observed in the microwave conductivity. In this case, the peak was understood as the composite effect of a very anisotropic superconducting gap on at least one of the superconducting bands with nodes, possibly on the electron pocket at the M point of the Brillouin zone, combined with a rapid decrease in the inelastic scattering rate with decreasing temperature T. In this paper, we show that the thermal conductivity peak also follows from the same model. These results point to a commonality with the cuprates and, as in that instance, is evidence for an electronic mechanism. In such a mechanism, the fluctuation spectrum responsible for the scattering and pairing glue becomes gapped with the onset of superconductivity, and consequently, the low temperature inelastic scattering rapidly tends to zero.