Effective interactions and transport properties of degenerate spin-polarized³He-⁴He mixtures

Abstract

We present calculations of the thermal conductivity, viscosity, and longitudinal spin diffusion of degenerate³He-⁴He mixtures as a function of spin polarization. Physical arguments and sum rules are used to describe qualitatively the behavior of the effective interactions between two³He quasiparticles. A recently proposed potential model is consistent with these expectations and provides the momentum- and polarization-dependent transition probabilities that enter into transport calculations. In the limit of small³He concentrations, our results agree with previous calculations based on the hard sphere model. For concentrations nearing saturation, however, we find structure in the thermal conductivity as a function of polarization with the³He density kept fixed. While the behavior of the viscosity remainsqualitatively similar to that at low concentration, the spin diffusion coefficient is qualitatively different. This behavior of the transport coefficients is largely a consequence of the strongly polarization dependentm _z =1 triplet scattering rate which becomes comparable to that in the singlet channel at large polarizations.