Nonlinear field-dependence and f-wave interactions in superfluid 3He

TL;DR

This study investigates the nonlinear magnetic field dependence of transverse acoustic Faraday rotation in superfluid ^{3}He-B, revealing new insights into f-wave pairing interactions and the limits of existing theoretical models.

Contribution

It provides the first detailed measurements of Faraday rotation at high fields and frequencies, identifying nonlinear effects and refining the theoretical understanding of superfluid ^{3}He-B.

Findings

Faraday rotation as large as 1710° observed

Attractive f-wave pairing interaction at 6 bar pressure

Nonlinear field dependence of Faraday rotation at high frequencies

Abstract

We present results of transverse acoustics studies in superfluid ^{3}He-B at fields up to 0.11 T. Using acoustic cavity interferometry, we observe the Acoustic Faraday Effect for a transverse sound wave propagating along the magnetic field, and we measure Faraday rotations of the polarization as large as 1710^{\circ}. We use these results to determine the Zeeman splitting of the Imaginary Squashing mode, an order parameter collective mode with total angular momentum J=2. We show that the pairing interaction in the f-wave channel is attractive at a pressure of P=6 bar. We also report nonlinear field dependence of the Faraday rotation at frequencies substantially above the mode frequency not accounted for in the theory of the transverse acoustic dispersion relation formulated for frequencies near the mode. Consequently, we have identified the region of validity of the theory allowing us to make corrections to the analysis of Faraday rotation experiments performed in earlier work.