Imaginary Squashing Mode Spectroscopy of Helium Three B

TL;DR

This study precisely measures the frequency of the J=2 imaginary squashing mode in superfluid helium-3 B, revealing detailed insights into its collective excitations through acoustic interference techniques.

Contribution

The paper introduces high-precision measurements of the collective mode frequency in superfluid helium-3 B using interference of transverse sound, providing new experimental data on order parameter dynamics.

Findings

Precise mode frequency measurements with 0.1-0.25% resolution

Identification of strong attenuation at mode crossing

Use of transverse sound interference for superfluid spectroscopy

Abstract

We have made precision measurements of the frequency of a collective mode of the superfluid 3He-B order parameter, the J=2- imaginary squashing mode. Measurements were performed at multiple pressures using interference of transverse sound in an acoustic cavity. Transverse waves propagate in the vicinity of this order parameter mode owing to off-resonant coupling. At the crossing of the sound mode and the order parameter mode, the sound wave is strongly attenuated. We use both velocity and attenuation measurements to determine precise values of the mode frequency with a resolution between 0.1% and 0.25%.