The theory of ultrasonic absorption in a superconductor

Abstract

The theory of ultrasonic absorption in a superconductor is treated by a method that is similar to that commonly used for analogous problems in superfluid helium, namely in terms of a pair of coupled equations, one of which is the superfluid equation of motion and the other is a Boltzmann equation describing the behaviour of the excitations. The results obtained for the attenuation of both longitudinal and transverse waves are in accord with accepted theory. The present treatment gives a detailed picture of the processes occurring in a sound wave in a superconductor, and emphasizes the close similarity that exists in simple cases between a superconductor and superfluid helium.