Ultrasonic Attenuation in Superconductors Containing Magnetic Impurities

Abstract

The Abrikosov-Gor'kov theory for a superconductor with magnetic impurities is applied to the calculation of attenuation coefficients. In this calculation several electronic time-dependent correlation functions are evaluated, and these functions are then used to evaluate the attenuation. In the limit of low sound-wave frequencies, the resulting coefficients are expressed in terms of a single energy integral. The physical significance of the result is discussed in terms of an effective density of "normal electrons" and energy-dependent mean free paths. Then, the attenuation is evaluated in the limit of low temperatures for superconductors both with and without an energy gap.