Analysis of Strong-Coupling Parameters for Superfluid 3He

Superfluid ³He 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 β-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 β-coefficients, β ₃₄₅, β ₁₂, β ₂₄₅, and β ₅ are calculated and comparison is made with theory.