Analysis of Strong-Coupling Parameters for Superfluid 3He

TL;DR

This paper investigates the strong-coupling effects in superfluid helium-3 by analyzing deviations in Ginzburg-Landau parameters, providing new pressure-dependent measurements of key coefficients and comparing them with theoretical predictions.

Contribution

It presents new experimental results for pressure dependence of specific Ginzburg-Landau coefficients in superfluid helium-3 and compares these with existing theoretical models.

Findings

Deviation of $g_z$ from weak-coupling is negligible at all pressures.

New pressure-dependent data for four combinations of $eta$-coefficients.

Comparison shows partial agreement with theoretical predictions.

Abstract

Superfluid $^{3}$He experiments show strong deviation from the weak-coupling limit of the Ginzburg-Landau theory, and this discrepancy grows with increasing pressure. Strong-coupling contributions to the quasiparticle interactions are known to account for this effect and they are manifest in the five $\beta$-coefficients of the fourth order Ginzburg-Landau free energy terms. The Ginzburg-Landau free energy also has a coefficient $g_{z}$ to include magnetic field coupling to the order parameter. From NMR susceptibility experiments, we find the deviation of $g_{z}$ from its weak-coupling value to be negligible at all pressures. New results for the pressure dependence of four different combinations of $\beta$-coefficients, $\beta$_{345}, $\beta$_{12}, $\beta$_{245}, and $\beta$_{5} are calculated and comparison is made with theory.