Anomalous attenuation of longitudinal ultrasound in intermediate state of high pure type I superconductor

TL;DR

This paper reports an anomalous dependence of ultrasonic attenuation on magnetic field direction in the intermediate state of a high-purity Gallium superconductor, linked to Fermi surface anisotropy.

Contribution

It reveals a novel anisotropic ultrasonic attenuation behavior in the intermediate state of a superconductor, explained by Fermi surface anisotropy.

Findings

Ultrasonic attenuation varies anomalously with magnetic field direction.

The phenomenon is specific to the intermediate state, not the normal state.

Fermi surface anisotropy accounts for the observed behavior.

Abstract

The dependence of the ultrasonic attenuation on the direction of magnetic field in an intermediate state of the very pure Gallium single crystal, in the case, when the magnetic field H is perpendicular to the wave vector k at the temperature T = 0.5 K, is found to be anomalously different from the dependence, observed at the same temperature and the magnitude of magnetic field equal to the critical magnetic field H=Hc in a normal state of superconductor. This new phenomenon can be explained, considering the anisotropy of the Fermi surface in the very pure Gallium single crystal.