Thermal Conductivity of Indium-Thallium Alloys in the Normal and Superconducting States

Abstract

Thermal conductivity measurements have been made on three indium-thallium alloys between 0.15\ifmmode^\circ\else\textdegree\fi{} and 0.8\ifmmode^\circ\else\textdegree\fi{}K. Temperature gradients were measured using carbon resistance thermometers. The alloys were of the type which show an increase in thermal conductivity on entering the superconducting state. At temperatures below 1\ifmmode^\circ\else\textdegree\fi{}K the superconducting state thermal conductivity decreases rapidly with decreasing temperature, becoming roughly proportional to ${T}^{3}$ and to the grain size in the specimens at the lowest temperatures. The data are interpreted as meaning that phonon conductivity limited by boundary scattering is important in this region.