Low-Temperature Thermal Conductivity and Specific Heat of Plastically Deformed High-Purity Tantalum Single Crystals

Abstract

The thermal conductivity and the specific heat of plastically deformed, high-purity tantalum single crystals have been measured together with an amorphous SiO2 specimen in the temperature range between 50 mK and about 2 K. After plastic deformation, the thermal conductivity was reduced by a factor of more than 100 and had a magnitude comparable to that of the amorphous SiO2 specimen. However, the specific heat measurements revealed a T3-relationship for the phonon contribution down to the lowest temperatures with a magnitude as in the case of undeformed crystalline solids. Thus, it must be concluded that the scattering of thermal phonons introduced by the plastic deformation has to be attributed to intrinsic properties of dislocations rather than to the interaction of phonons with tunneling systems. In the present paper the scattering mechanism is related to oscillations of geometrical kinks in non-screw dislocations.