Ultrasonic attenuation of metals at low temperatures

At very low temperatures when the mean free path of the electrons in metals becomes large but less than the wavelength of sound wave a relationship between electrical conductivity and attenuation in the normal state has been deduced byMason using the mean free path associated with the electrical conductivity. Similarly, a relationship between thermal conductivity and attenuation can be deduced using the mean free path associated with the thermal conductivity. It has been shown from experimental results that the relationship thus deduced agrees better in the temperature region discussed in the paper. When the mean free path becomes greater than the wavelength, α_s/α_n, the ratio of superconducting attenuation to that in the normal state can be determined in accordance with the theory ofBardeen, Cooper andSchrieffer. It is apparent from experimental results that in the limited region where the scattering of electrons is predominantly by lattice vibrations, K_s/K_n, the ratio of superconducting thermal conductivity to that in the normal state is equal to α_s/α_n.