Wave Acoustics for Propagation of Ultrasound along a Vortex Array in Superfluid3He

摘要

A wave-acoustics theory has been developed to describe the propagation of zerosound parallel to vortex lines in rotating (3)He. The authors show that a diffraction 'shadow' is formed in which the wave amplitude is suppressed by interference around vortices. The phenomenon contributes to the experimentally observed effect of rotation on the sound amplitude and exceeds the attenuation at large core radii. The dependence of the diffraction contribution on the angular velocity changes drastically at the transition from vortices with a finite core to coreless vortices when the magnetic field is decreased to zero. The authors derive conditions for the applicability of the classical geometrical acoustic method in describing zero sound propagation in a vortex array.