Lattice thermal conductivity of cold-worked noble-metal alloys between 0.5 and 4 K

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Abstract
Thermal-conductivity measurements were made for two Cu-, two Au-, and one Ag-based polycrystalline rods and one Cu-based single-crystal rod in the temperature range 0.5 to 4 K. The polycrystalline rods were measured with each rod first being in a highly cold-worked condition and then in various stages of recovery brought about by annealing at temperatures up to 1000 K. From the total measured conductivity, the lattice conductivity was extracted by calculating the electronic component using the Wiedemann-Franz law and electrical-resistivity measurements. In all the cold-worked alloys, the lattice conductivity did not have the temperature dependence expected from standard theory. Comparable experimental results, which have been published only for Cu alloys and only above 1.5 K are in agreement with our results. The measurements below 1.5 K indicated an even larger departure from standard theory. In the entire temperature region (0.5 to 4 K), our belief is that the anomalies are contained in that part of the lattice conductivity which is limited by dislocation scattering. The anomalies in the Ag- and Au-based alloys, though basically similar to those in Cu-based alloys, occurred at different temperatures. The results were unified by recognizing that the phonon wavelengths were the same at corresponding temperature of the anomalies.