Giant Viscosity Enhancement in a Spin-Polarized Fermi Liquid

Abstract

The viscosity is measured for a Fermi liquid, a dilute 3 He-4 He mixture, under extremely high magnetic field/temperature conditions (B ≤ 14.8 T, T ≥ 1.5 mK). The spin splitting energy µB is substantially greater than the Fermi energy kBTF ; as a consequence the polarization tends to unity and s-wave quasiparticle scattering is suppressed for T ≪ TF . Using a novel composite vibratingwire viscometer an enhancement of the viscosity is observed by a factor of more than 500 over its low-field value. Good agreement is found between the measured viscosity and theoretical predictions based upon a t-matrix formalism.

Anisotropic Spin Diffusion in Trapped Boltzmann Gases

“…The theoretical explanation [3]- [8] for this behavior is based on the two states playing the role of a pseudo-spin-1/2 system, having transverse spin waves. The theory of these new effects is based on old ideas of the transport properties of polarized homogeneous quantum gases of real spins, such as 3 He gas and solutions of 3 He in liquid 4 He, [9], [10] transcribed to the trapped gas pseudo-spin case.…”

“…[9] Moreover, Fomin [12] has suggested the effect should not exist. However, a recent experiment [9] has overcome several possible experimental objections and finds good agreement with theory. Moreover Mineev has very recently presented theoretical analysis that questions the validity of Fomin's approach.…”

“…( 16) is the hydrodynamic frequency as modified by spin rotation. [9], [10], [15]. The first term is the effective diffusion frequency while the second is the dipole-mode pseudo-spin-wave frequency.…”

“…Besides spin waves, the theory for homogeneous polarized fermions or bosons led to the prediction of anisotropic spin diffusion in the degenerate state. [9], [10], [11] When a spin nonuniformity is longitudinal, that is, with a variation in the magnitude of the magnetization, the spin diffusion coefficient is D . On the other hand, in a spin-echo experiment, the magnitude of the magnetization is uniform but it varies spatially in direction.…”

“…Experimentally this feature has been seen, but was not always in reasonable accord with theory. [9] Moreover, Fomin [12] has suggested the effect should not exist. However, a recent experiment [9] has overcome several possible experimental objections and finds good agreement with theory.…”