Low-temperature internal friction and thermal conductivity in plastically deformed metals due to dislocation dipoles and random stresses

Abstract

The contribution to the low frequency internal friction and the thermal conductivity due to optically vibrating edge dislocation dipoles is calculated within the modified Granato-Lucke string model. The results are compared with the recent experiments on plastically deformed samples of Al, Ta and Nb at low temperatures. It is shown that the presence of a reasonable density of optically vibrating dislocation dipoles provides a good fit to the thermal conductivity in superconducting samples. At the same time, the internal friction experiments can not be described within the standard fluttering string mechanism. We found that the problem can be solved by assuming random forces acting on the dislocation dipoles. This gives an additional contribution to the internal friction which describes well the experimental data at low temperatures while their contribution to the thermal conductivity is found to be negligible.