Theory of Pure Type-II Superconductors in High Magnetic Fields. II. Ultrasonic Attenuation

Abstract

We propose here a theory of pure type-II superconductors in high magnetic fields. Making use of the guess that the effect of the magnetic field on a pure type-II superconductor in a high field is similar to that of a transport current, we circumvent the difficulty associated with the expansion in powers of the order parameter $\Delta$. As an application of this conjecture, we calculate here the ultrasonic attenuation coefficients in the gapless region of a pure type-II superconductor. The attenuation coefficients decrease sharply in the superconducting region as ${(H_{c2\mathrm{}}-H)}^{\frac{1}{2}}$, where $H$ is the external field, and are strongly anisotropic—a simple manifestation of the anisotropy in the excitation spectrum of quasiparticles.