VISCOSITY OF LIQUID HE-3-HE-4 MIXTURES AT VERY-LOW TEMPERATURES

We have investigated the viscosity eta of He-3-He-4 mixtures with the vibrating wire technique at various He-3-concentrations (0.98% less-th an-or-equal-to x less-than-or-equal-to 9.5%) in the temperature range 1 mK less-than-or-equal-to T less-than-or-equal-to 100 mK and at press ures 0 bar less-than-or-equal-to p less-than-or-equal-to 20 bar. The t emperature dependence of the viscosity predicted by the Landau theory for Fermi liquids (etaT2 = const. at T much-less-than T(F)) is confirm ed at T < 10 mK at all concentrations and pressures. The absence of a pressure dependence of the viscosity is in strong discrepancy to the t heoretical prediction of Hsu and Pines [1]. However we can explain our results by taking into account the He-3-quasiparticle interaction pot ential derived from recent measurements of the solubility of He-3 in H e-4 in the same temperature and pressure ranges [2].