Thermal Conductivity of Superconducting Indium Alloys near the Upper Critical Field

The thermal conductivity of several indium-bismuth specimens has been measured as a function of magnetic field and temperature between 0.3 and 4.2°K. The main emphasis is on the region near the upper critical field, where a linear variation of the electronic thermal conductivity with magnetic field is expected. The experimental results are in good agreement with the calculations of Caroli and Cyrot above a reduced temperature of 0.4, but, below that temperature, the experimental values of the slope are lower than the theoretical values by up to 30%. It is possible to account for the discrepancy by assuming a more rapid variation with temperature of the parameter $\frac{{\kappa }_2}{\kappa }$ than that which is theoretically expected. For the comparison with theory, it was necessary to separate the electronic and lattice conductivities, and to analyze the lattice term into its contributions from the various scattering mechanisms. A correction could then be made for the field variation of the lattice conductivity. From the critical fields, the product of the electronic mean free path and the residual electrical resistivity was determined to be 0.56×${10}^{-11\mathrm{}}$ Ω ${\mathrm{cm}}^2$. The data also lead to a value for the coherence length of indium of 3540 Å.