Measuring Corrections to the Amplitude Mode Masses in Superfluid ³He

Superfluid ³He has a rich spectrum of collective modes with both massive (gapped) and massless (gapless) excitations. The masses of these modes can be precisely measured with acoustic spectroscopy and fit to theoretical models to extract interaction strengths of the underlying superfluid. Prior comparisons between theory and experiment accounted for Fermi-liquid effects, f-wave interactions, and the strong-coupling energy gap. However, strong-coupling corrections to the mode mass itself were not included. In this work, we employ a simple procedure to incorporate these corrections^[1] to the mode which improve the determination of the f-wave pairing strength, (1/x₃). Results from several independent experiments are brought into better agreement with the improved theoretical model.

[1] J.J. Wiman, Ph.D. Thesis (2018)