Low-temperature thermal conductivity and specific heat of plastically deformed high-purity tantalum single crystals

The thermal conductivity and the specific heat of plasticity deformed, high -purity tantalum single crystals have been measured together,vith an amorph ous SiO2 specimen in the temperature range between 50 mK and about 2 K. Aft er plastic deformation, the thermal conductivity was reduced by a factor of mor e than 100 and had a magnitude comparable to that of the amorphous SiO 2 specimen. However, the specific heat measurements revealed a T-3-relation ship for the phonon contribution down to the lowest temperatures,with a mag nitude as in the case of undeformed med crystalline solids. Thus, it must b e concluded that the scattering of thermal phonons introduced by the plasti c deformation has to be attributed to intrinsic properties of dislocations rather than to the interaction of phonons, with tunneling systems. In the p resent paper the scattering mechanism is related to oscillations of geometr ical kinks in non-screw dislocations.